Same player with a different username

[wrldtrvllr]

I've just found myself playing a game against a player who I had previously red-thumbed. They apparently closed their former account, and created a new one with an almost identical username. Is it legitimate for a user to change names in this way?

[voriki]

I had posted the same reply on this thread concerning double accounts.
While my first part handles about the ELO, and other ways of cheating, I do end with mentioning the same type of situation as you mention.

I have an alt account named 'Voriki alt', and only played 2 TRAINING games against myself. No ELO involved, so this is legal.
But if you play against(or with) your alt account on normal matches or arena, where scores matter, then it be logical to not be allowed.

And even if both accounts don't play the same games, but always different tables, technically no harm done ELO-wise, but you'd be sort of evading red thumbs.
Assume main account was red thumbed by someone, and then the alt account plays a match against the same player, this should normally not be allowed, since the player said he no longer wants to play against the first player in any way, this includes alt accounts.