Usernames can be very valuable though. If it's a story about Delicious, I'd like to see joshu's comments. If it's about Google search, I'll be looking for Matt Cuts.
I do like the first idea though. It would be a loose indicator of quality without giving too much away.
Well, It is true, but they are exceptions, not the rule.
Potential solutions
1. If the author feels like he is the authority and/or is the important part of the comment, he can always declare it in the comment itself. (The profile-link can always be verified by the users, to ensure that any such claim is correct.)
2. or you can click the links of the comments.
3. or even there might a functionality implemented to show all the usernames on the thread (by default, the author names would not be shown). Later PG can see, if default off makes sense, based on the data captured and user trends (eg. if 99% people are always want to see the commenter name) .
I do like the first idea though. It would be a loose indicator of quality without giving too much away.