Heh. I didn't realize that Comments/unread was subscriber-only. Yeah. It would be very hard to follow this conversation without it.
Before Comments/unread was available someone made a greasemonkey script to highlight new comments in lwn threads. I used it for a while.
To be honest, though, this is an absurdly long thread for lwn.net. Most articles rarely breach 50 comments. And lwn.net isn't really a 'social networking' or 'community' site (I'd never pay for one).
It's primary purpose is as a news publication, and while it does do 'aggregation' and announcement publishing, the real value of the site comes from the in-depth articles they produce, by doing real reporting (interviewing people involved, digging through mailing lists, source files, changelogs, etc). Nobody else in our esoteric little community is doing anything like it, and it's what makes lwn.net worth paying for, imho.
Using avatars, etc. would be giving way too much importance to the comments section of the site, which like the 'aggregation service,' is a secondary component. Again, imho.