If we were to enable blocking of specific users from commenting on your posts, I think we would also need to make the list of users that you block public. Also, I think the block would only function on your own posts, and not on replies to your comments on other’s posts. The question IMHO, is whether what is gained from this is worth what is lost. Trolling will be greatly diminished, which would be a boon; however, I wonder if people will avoid users that ban too liberally, which would be an important counter to abusive blocking. I like that the system puts power in the hands of hubskiers, but I wonder to what extent the community would allow it to be abused. Importantly, I don’t think a poster should be able to delete another’s comments. The most they could do is prevent future ones.
One other thought: although you might not see the ignored comment, everyone else does, and therefore it can still disrupt the conversation.