I missed this thread originally, but let me answer your question a bit late.

do people actully believe that tilly had to post as Anonymous? why could he not post as bluebell?

I believed (still do in fact) that my posting style is distinctive enough that any alternate account would have quickly been recognized to be me. In fact a couple of people made a game of figuring out which anonymous posts were me, and would email me as they spotted them. (They caught a surprising portion and weren't often wrong.)

Identity in an online forum is more complex than you would think.