I’d like to be able to follow forum activity using an RSS reader (to avoid having to come to the website every day to stay on top of the forum), but it seems like the current RSS feed only includes new posts, not comments.
Is it possible to modify the configuration of the forum software so that it includes comments in the feed?
that's a good point. I've been looking for a way to do this some time ago, but it seemed that this is the price we have to pay for the flexibility of drupal. The comments to forum topics are handled the same way as comments to articles, pages etc. ("everything is a node").
What you can do is to subscribe to the comment RSS feed http://tech.knime.org/crss which contains all comments to all topics. I know that this is not optimal and yet another separate feed to subscribe, but that's the best solution I have to offer so far.
I'll keep you posted if I find a better way to handle the comments.