greaterwrong has them:
Feeds for just the comments, just the posts, or both comments and posts, of an individual user (for example, here’s Eliezer Yudkowsky’s comments feed); these are accessible from the user’s page (e.g., here’s Eliezer Yudkowsky’s page)
Go to the frontpage, hover-over the different filters (curated, frontpage, community, etc) and click on the rss button in the hover-over, to get the respective rss url.
As I mentioned in a post that has now fallen off the end of meta: while RSS feeds work much better now, usernames still don't show up as the author in the feeds.
Yeah, this is on my radar to fix. It should probably be pretty straightforward to fix, so a PR on our Github is also welcome.
Just pushed a fix that should make RSS feeds work properly (you will have to resubscribe to the RSS feeds, if you did so a while ago). Thanks to squirrelInHell who made me aware of the deeper problems with our RSS feed (that my RSS reader seemed to mostly automatically patch, but which other people ran into).