I agree wholeheartedly with #1 — and they should be collapsible too! Actually, they should probably start that way, for easy reading, but I don’t see that happening as it is the commenting aspect that allows Buzz to stand out as a conversational platform. That’s why #2, at least in the native Buzz platform, may not be likely to happen — Google needs comments to push items to the top to keep people engaged. I think this will probably change in the new clients that will be developed, much like what happened with Twitter, but that may take a bit.
As for tracking, that would be cool. It may make it so I don’t have to mute conversations all day long. Categorical and favourite tracking would be perfect! And better integration with other social media sites is most definitely a must. I don’t think Google will be putting the branding of other companies in there though, but that is another thing that will likely appear in custom clients and widgets/scripts.