I do reserve the right to delete comments if they aren't sticking to the topic at hand. I'll live if we don't agree, but you don't get to be snotty with me and go off topic. My blog, my rules.
I also add a response to each comment that comes through - I do not change anything the original commenter writes; I just add to the end. I find that I can keep track of people a little bit better that way.
I do also reserve the right to ban individuals from my comments if they display behavior that I'm not down with. (In other words, if you piss me off enough because you don't play fair, you're not allowed to comment.)