diff --git a/app/containers/markdown/Markdown.textStyle.test.tsx b/app/containers/markdown/Markdown.textStyle.test.tsx
index ae7b1b4af12..c25835e5435 100644
--- a/app/containers/markdown/Markdown.textStyle.test.tsx
+++ b/app/containers/markdown/Markdown.textStyle.test.tsx
@@ -40,4 +40,30 @@ describe('Markdown textStyle integration', () => {
 
 		expect(onLinkPress).toHaveBeenCalledWith('https://rocket.chat');
 	});
+
+	it('propagates custom color in textStyle to link, mention, hashtag and plain text', () => {
+		const onLinkPress = jest.fn();
+		const textStyle = { color: 'red' };
+
+		const { getByLabelText, getByText } = render(
+			<Markdown
+				msg='hello [my link](https://rocket.chat) @rocket.cat #general'
+				textStyle={textStyle}
+				onLinkPress={onLinkPress}
+				mentions={[{ _id: 'u1', username: 'rocket.cat', name: 'Rocket Cat', type: 'user' }]}
+				username='another.user'
+				channels={[{ _id: 'r1', name: 'general' }]}
+			/>
+		);
+
+		const plainTextNode = getByLabelText('hello ');
+		const linkNode = getByText('my link');
+		const mentionNode = getByText('@rocket.cat');
+		const hashtagNode = getByText('#general');
+
+		expect(plainTextNode.props.style).toEqual(expect.arrayContaining([expect.objectContaining({ color: 'red' })]));
+		expect(linkNode.props.style).toEqual(expect.arrayContaining([expect.objectContaining({ color: 'red' })]));
+		expect(mentionNode.props.style).toEqual(expect.arrayContaining([expect.objectContaining({ color: 'red' })]));
+		expect(hashtagNode.props.style).toEqual(expect.arrayContaining([expect.objectContaining({ color: 'red' })]));
+	});
 });
diff --git a/app/containers/markdown/components/inline/Link.tsx b/app/containers/markdown/components/inline/Link.tsx
index 8bc9ea9d527..4da2c3124d8 100644
--- a/app/containers/markdown/components/inline/Link.tsx
+++ b/app/containers/markdown/components/inline/Link.tsx
@@ -49,7 +49,7 @@ const Link = ({ value }: ILinkProps) => {
 
 	return (
 		<Text
-			style={[styles.link, ...(textStyle ? [textStyle] : []), { color: themes[theme].fontInfo }]}
+			style={[styles.link, { color: themes[theme].fontInfo }, ...(textStyle ? [textStyle] : [])]}
 			onPress={handlePress}
 			onLongPress={onLongPress}>
 			{(block => {
diff --git a/app/containers/markdown/components/mentions/AtMention.tsx b/app/containers/markdown/components/mentions/AtMention.tsx
index bb454b7bbd2..ae3fcfdfed0 100644
--- a/app/containers/markdown/components/mentions/AtMention.tsx
+++ b/app/containers/markdown/components/mentions/AtMention.tsx
@@ -28,10 +28,10 @@ const AtMention = memo(({ mention, mentions, username, navToRoomInfo, useRealNam
 			<Text
 				style={[
 					styles.mention,
-					...(textStyle ? [textStyle] : []),
 					{
 						color: themes[theme].statusFontService
-					}
+					},
+					...(textStyle ? [textStyle] : [])
 				]}>
 				{preffix}
 				{mention}
@@ -76,7 +76,7 @@ const AtMention = memo(({ mention, mentions, username, navToRoomInfo, useRealNam
 		return (
 			// not enough information on mentions to navigate to team info, so we don't handle onPress
 			<Text
-				style={[styles.mention, ...(textStyle ? [textStyle] : []), mentionStyle]}
+				style={[styles.mention, mentionStyle, ...(textStyle ? [textStyle] : [])]}
 				onPress={atMentioned?.type === 'team' ? undefined : handlePress}>
 				{preffix}
 				{text}
@@ -85,7 +85,7 @@ const AtMention = memo(({ mention, mentions, username, navToRoomInfo, useRealNam
 	}
 
 	return (
-		<Text style={[styles.text, ...(textStyle ? [textStyle] : []), { color: themes[theme].fontDefault }]}>{`@${mention}`}</Text>
+		<Text style={[styles.text, { color: themes[theme].fontDefault }, ...(textStyle ? [textStyle] : [])]}>{`@${mention}`}</Text>
 	);
 });
 
diff --git a/app/containers/markdown/components/mentions/Hashtag.tsx b/app/containers/markdown/components/mentions/Hashtag.tsx
index 3336998369c..425779204e7 100644
--- a/app/containers/markdown/components/mentions/Hashtag.tsx
+++ b/app/containers/markdown/components/mentions/Hashtag.tsx
@@ -57,10 +57,10 @@ const Hashtag = memo(({ hashtag, channels, navToRoomInfo }: IHashtag) => {
 			<Text
 				style={[
 					styles.mention,
-					...(textStyle ? [textStyle] : []),
 					{
 						color: themes[theme].fontInfo
-					}
+					},
+					...(textStyle ? [textStyle] : [])
 				]}
 				onPress={handlePress}>
 				{`${preffix}${hashtag}`}
@@ -68,7 +68,7 @@ const Hashtag = memo(({ hashtag, channels, navToRoomInfo }: IHashtag) => {
 		);
 	}
 	return (
-		<Text style={[styles.text, ...(textStyle ? [textStyle] : []), { color: themes[theme].fontDefault }]}>{`#${hashtag}`}</Text>
+		<Text style={[styles.text, { color: themes[theme].fontDefault }, ...(textStyle ? [textStyle] : [])]}>{`#${hashtag}`}</Text>
 	);
 });
 
diff --git a/app/i18n/locales/en.json b/app/i18n/locales/en.json
index 8f9606fe55d..37de79125da 100644
--- a/app/i18n/locales/en.json
+++ b/app/i18n/locales/en.json
@@ -1002,6 +1002,7 @@
   "User_not_found_or": "User not found or incorrect password",
   "User_sent_an_attachment": "{{user}} sent an attachment",
   "Username": "Username",
+  "Username_invalid": "Use only letters, numbers, dots, hyphens and underscores",
   "Username_is_already_in_use": "Username is already in use.",
   "Username_not_available": "Username not available",
   "Username_or_email": "Username or email",
diff --git a/app/views/ProfileView/index.test.tsx b/app/views/ProfileView/index.test.tsx
index 0fe9bc0cb4b..03a99c22511 100644
--- a/app/views/ProfileView/index.test.tsx
+++ b/app/views/ProfileView/index.test.tsx
@@ -9,6 +9,7 @@ import { twoFactor } from '../../lib/services/twoFactor';
 import handleSaveUserProfileError from '../../lib/methods/helpers/handleSaveUserProfileError';
 import EventEmitter from '../../lib/methods/helpers/events';
 import { setUser } from '../../actions/login';
+import I18n from '../../i18n';
 
 jest.mock('react-redux', () => ({
 	useDispatch: jest.fn()
@@ -69,7 +70,8 @@ const buildState = () => ({
 		Accounts_AllowUserAvatarChange: true,
 		Accounts_AllowUsernameChange: true,
 		Accounts_CustomFields: '',
-		Accounts_AllowDeleteOwnAccount: true
+		Accounts_AllowDeleteOwnAccount: true,
+		UTF8_User_Names_Validation: '[0-9a-zA-Z-_.]+'
 	}
 });
 
@@ -110,6 +112,27 @@ describe('ProfileView submit', () => {
 		expect(handleSaveUserProfileError).not.toHaveBeenCalled();
 	});
 
+	it('does not save when the username contains invalid characters', async () => {
+		const { getByTestId, findByText } = renderProfile();
+
+		fireEvent.changeText(getByTestId('profile-view-username'), 'cygnus b');
+		fireEvent.press(getByTestId('profile-view-submit'));
+
+		await findByText(I18n.t('Username_invalid'));
+		expect(saveUserProfile).not.toHaveBeenCalled();
+	});
+
+	it('saves when the username is corrected to a valid value', async () => {
+		(saveUserProfile as jest.Mock).mockResolvedValue(true);
+
+		const { getByTestId } = renderProfile();
+
+		fireEvent.changeText(getByTestId('profile-view-username'), 'cygnus.b');
+		fireEvent.press(getByTestId('profile-view-submit'));
+
+		await waitFor(() => expect(saveUserProfile).toHaveBeenCalledWith({ username: 'cygnus.b' }, {}));
+	});
+
 	it('asks for the current password before changing the email', async () => {
 		const { getByTestId } = renderProfile();
 
diff --git a/app/views/ProfileView/index.tsx b/app/views/ProfileView/index.tsx
index 6b4366d58da..34496096703 100644
--- a/app/views/ProfileView/index.tsx
+++ b/app/views/ProfileView/index.tsx
@@ -46,16 +46,25 @@ import ConfirmEmailChangeActionSheetContent from './components/ConfirmEmailChang
 const MAX_BIO_LENGTH = 260;
 const MAX_NICKNAME_LENGTH = 120;
 
+// Mirror the server's username validation, which matches the value against the
+// UTF8_User_Names_Validation setting anchored as a full match (`^pattern$`),
+// falling back to the default pattern when the setting is empty or invalid.
+// https://github.com/RocketChat/Rocket.Chat/blob/develop/apps/meteor/app/lib/server/functions/validateUsername.ts
+const DEFAULT_USERNAME_VALIDATION = '[0-9a-zA-Z-_.]+';
+
+const isValidUsername = (username: string, pattern: string): boolean => {
+	try {
+		return new RegExp(`^(${pattern || DEFAULT_USERNAME_VALIDATION})$`).test(username);
+	} catch {
+		// Fall back to the default pattern if the server provides an invalid regex.
+		return new RegExp(`^(${DEFAULT_USERNAME_VALIDATION})$`).test(username);
+	}
+};
+
 interface IProfileViewProps {
 	navigation: NativeStackNavigationProp<ProfileStackParamList, 'ProfileView'>;
 }
 const ProfileView = ({ navigation }: IProfileViewProps): ReactElement => {
-	const validationSchema = yup.object().shape({
-		name: yup.string().required(I18n.t('Name_required')),
-		email: yup.string().email(I18n.t('Email_must_be_a_valid_email')).required(I18n.t('Email_required')),
-		username: yup.string().required(I18n.t('Username_required'))
-	});
-
 	const { showActionSheet, hideActionSheet } = useActionSheet();
 	const { colors } = useTheme();
 	const dispatch = useDispatch();
@@ -67,6 +76,7 @@ const ProfileView = ({ navigation }: IProfileViewProps): ReactElement => {
 		Accounts_AllowUserAvatarChange,
 		Accounts_AllowUsernameChange,
 		Accounts_CustomFields,
+		UTF8_User_Names_Validation,
 		serverVersion,
 		user
 	} = useAppSelector(state => ({
@@ -77,9 +87,19 @@ const ProfileView = ({ navigation }: IProfileViewProps): ReactElement => {
 		Accounts_AllowUserAvatarChange: state.settings.Accounts_AllowUserAvatarChange as boolean,
 		Accounts_AllowUsernameChange: state.settings.Accounts_AllowUsernameChange as boolean,
 		Accounts_CustomFields: state.settings.Accounts_CustomFields as string,
+		UTF8_User_Names_Validation: state.settings.UTF8_User_Names_Validation as string,
 		serverVersion: state.server.version,
 		Accounts_AllowDeleteOwnAccount: state.settings.Accounts_AllowDeleteOwnAccount as boolean
 	}));
+
+	const validationSchema = yup.object().shape({
+		name: yup.string().required(I18n.t('Name_required')),
+		email: yup.string().email(I18n.t('Email_must_be_a_valid_email')).required(I18n.t('Email_required')),
+		username: yup
+			.string()
+			.required(I18n.t('Username_required'))
+			.test('valid-username', I18n.t('Username_invalid'), value => isValidUsername(value ?? '', UTF8_User_Names_Validation))
+	});
 	const isMasterDetail = useMasterDetail();
 	const {
 		control,