Re: the blogging style thing
My decision to leave a comment or create a new thread would more likely than not be based on whether or not my opinion introduces a new "commentable" issue. The fact that I put it in my blog means that I'm prepared to comment further on it without polluting the other bloggers thread. Pingbacks/Trackbacks make it easy enough to trace the origins of a thread if you are dedicated enough.
Also, commenting on other peoples blogs is inconventient because you have to manually go back and check whether you've been flamed :P or not :-) It would be good if you could subscribe to threads to receive notifications that new comments have been added while the conversation is still active.