Yeah, you would need a way to filter out spam. I was thinking that maybe it's the responsibility of the owner of the blog to maintain a list of legit comments... They would have to regularly scan the chain for... yeah this is getting tedious... nvm that.
Agreed, my concern was when using a protocol to link comments together.
I guess from this point is to actually start implementing it to really grasp the limitation of different approach. Thanks for the brainstorm @rob.