Nah that's not doxing, that's people's username, they're meant to be shown, that's why they name themselves stevie45 or something.
Not showing other people's username isn't really necessary, they agreed to be viewed when they left the public comment.
If you feel like not showing your username on screenshot to prevent trouble, cover it, you didn't prevent anyone else from stumbling upon the original post and taking the screenshot of you, so that's fair.
I suppose you can be a full hypocritical f🅰️k and delete your post after taking the screenshot, if there's a rule to regulate down to being a hypocrite then this site isn't free so I'm not even putting up rules on it.
Being a hypocrite that gives no f🅰️k is actually pretty funny once you get down to the character, can you imagine that?