Hi there, @marr.
I believe this should have been posted either in Suggestions or included in the bug tracker, in case it hasn't been reported yet in that section. I totally understand that the problems you are presenting here are very obnoxious, but, as far as I know, this has been going on for years. Problems with usernames are relatively common, especially when it comes to the userlist and the friendlist. Hopefully, they are already working on it.
If you keep getting banned at certain chats, please contact the main owners to let them know you are not the person to whom the ID used to belong to. You can also do this by reporting an unfair ban, clicking on that option when getting banned will let you send a message to the main owner of that chat.
Best regards,
Norman.