Damn, it turns out version 1.0.3 of my script still doesn't display the discussion comments. After user evec pointed out the existence of http://lesswrong.com/r/all/new which shows all posts in both main and discussion, I thought that http://lesswrong.com/r/all/comments would similarly show comments in both sections, but it turns out it only shows main comments. So if you want to have the Power Reader display discussion comments as well, upgrade to 1.0.4. It loads up to 200 most recent main comments and 200 most recent discussion comments.