Your list at the beginning piqued my interest and got me thinking (and I'm sure you already know all of what I'm going to say, I just can't help but comment)...

#1 isn't particular to blogs, no? Perhaps the most defining trait is the canonical list of postings in time at that URI.

#2 I might reword as "syndication", wrapping up each post or an excerpt of that post "to go" in order to facilitate "subscription".

#3, I agree with that comments are part of the spirit of blogs, though there are certainly "blogs" that don't permit it. IMHO, the "ideal" blog should provide a mechanism for engaging the author publicly in a conversation relating to the original material.

Any plans to implement OpenID?