It doesn't really matter, he hasn't changed at all, it would be different if Taboo has some stuffty IRL issues which reflects themselves online, gets banned, and then comes back and actually changes his behavior. Taboo is just a bigger cunt every time he comes back, just with a little bit less basing under his feet.
And no, Taboo doesn't have any mental illness other than advanced-weeboo-friendry, he's just incredibly aggressive and hostile because he thinks putting other people down for no reason at all makes him popular. He's not even right in the overwhelming majority of his arguments.