If I try to post exactly the paragraph you wrote, the error only occurs under the following condition:
if the first character of the paragraph is in Persian and there is another Persian character (whether with or without a space) immediately before the username, then the issue I mentioned will happen, and the @ symbol will appear on the right side of the username.
Two images have been shared: in one you can see the text as written in the composer, and in the other you can see how the same text is displayed in the forum
