It's not that he -wanted- to avatar Belcoot. It's that Belcoot is an avatar character traditionally associated to Gate. So, it's good form to actually ask if he minds you to avatar Bel. There's also the thing that it can be somewhat confusing to others due to association (someone else avataring Shady Thousand could be often confused with Elfboy, for instance, even though he's not avataring him right now).
Yeah, just gonna echo this, even though the issue is past. We've had situations where others have used avatars associated with certain people in the past, and it has led to confusion. Like I remember Laggy, unknowingly, took a Zio avatar that was the exact same pic as one super has used several times in the past, and it caused confusion. Another was when Rosa Aquafire used Clear Tranquil's Peppita avatar.
And then there was the scenario where super and Ciato specifically swapped Avatars (one of them used Fuijin, the other...fuck if I can remember!) just to confuse everyone.
Yeah, avatars are just good visual cues to associate with someone. In the case of Djinn "stealing" Repede from Trips, his pic was so drastically different in a number of ways, it was easy to distinguish the fact that this was Djinn, not Trips.
Oh yeah, and then there was that one moment where like 5 DLers started explicitly copying Avatars of OTHER people as they were avataring them! This led to an amusing punishment <_< >_>