For whatever their reasons maybe, I've seen a few users had their usernames changed, However, their old edited posts still shows their previous usernames, and that in my opinion to some extent beats the purpose of having their name changed initially.
I'm sorry, If I'd be tying anyone to old names (against their wishes), I'll edit this post and close the thread as soon as I get a response.
It shows both on PC and Mobile
https://bitcointalk.org/index.php?topic=5193409.msg52776379#msg52776379
https://bitcointalk.org/index.php?topic=5162407.msg51730338#msg51730338
