Support custom controllers for comments

I'd like very much to give comments their own controller. Users should be able to control the logic of what's happening a bit more from within their template, I think. For instance, I might like a widget (visible only when their are multiple child comments), which toggles the collapse of the child widgets. I wouldn't want to build this right in, because that would impose dependencies and generally suck. But it's a simple task to support it, or it should be.