I think it might actually be a good idea to give any poster the power to delete replies in their post's comments thread - Facebook does this automatically and I don't think it's a problem in real life, except of course for the trolls themselves - but that would require development resources, and as ever, we have none.

If you feel that going to those lengths are necessary, here is a more palatable censorship technique which might achieve the intended effect - instead of the current troll feeding penalty, simply automatically delete heavily down-voted comments. That way the community collectively decides what is inappropriate and what is simply discussion, rather than the OP.