I don't call it writers behaving badly, though. Writers using their characters as a personal mouthpiece is nothing new, and Gillen and several other examples just do it a tad stronger than anyone else.
Also, the original comment suggested Gillen should have just made this an autobiographical book - but it basically is. Gillen has developed beyond his personal perceptions of music, it seems, in writing the Singles Club issues, but for Rue Britannia, it deals largely with Britpop and the like, which Gillen experience firsthand, therefore, self-insertion is basically necessary. I just view it as Gillen not being egotistical enough not to name the lead after himself, given that's what everyone would accuse him of, what with Kohl's saving the world and the like.
Everybody does self-insertion, to some degree. Ben Grimm reflects Jack Kirby, and there's dozens of other examples.