Can one get an RSS feed for specific topics here? (I looked but did not see a way.)

It's a feature on Reddit, and being able to subscribe to something such as listings of books, music, etc. would be handy.

Then if someone wants to pose the question again they can refer to the initial posting and ask people to add their comments there.

Yes, and it's the kind of thing searching was invented for. But for some reason HN refuses to provide a way to search posts and comments (no, having to go to Google and search news.ycombinator.com is not decent search. Google doesn't take into consideration how long ago a post was, how many comments it had and how many votes it received, all information I think is useful for determining relevance of the results).