What will happen to anew user's account if he wishes to change his username after some months in the forum?
If the user has achieved a high rank in the forum, and choses to change his username, will the account be suspected of changing hand and be tagged for that? If yes how will other users know he is still the rightful owner?
If followed the appropriate forum guides on the profile edit and you're sure of rightfully owning the account then then there's no necessary of suspecting the account but after done processes at a current run there's some contexts of post changes either on writing patterns or posting on different boards which the formal Identified user (change of name) is usual, then there's every possiblities of the account to drag other users attentions which then it may be suspicious and tantamount to be tagged. It absolutely means impersonation.
But (and let me know if I'm wrong) afaik, although it is not often looked favourably on selling accounts, it is not forbidden either; and, on the other hand, impersonation would be if someone maintained the old owner's username and pretended to be him/her, which is the contrary of what the OP is asking.
So there is no need to split hairs here. The only real problem is that it won't be easy to see your request fulfilled, but forger about being tagged for no reason.