It isn’t a bug precisely, it is a combination of weird symbols… which idk just behaves in weird way like that invisible whitespace character. I think it got reported and replit team deleted the comments which had those characters pasted in it. If you see such comments in future I would recommend to report them using report button.
It looks like some troll was spamming unicode characters on the forum. Combining character - Wikipedia.
these characters are supposed to put diacritics like ¨ and ˆ over letters, but some bored guy was stacking them. Just treat this as ordinary spam/trolling comments.