I want to do it for my own use (I read every single post). I want to read the posts in the feed w/o that extra click every time. My forum's personal and I only have 10-12 friends using it anyways.
The purpose of the rss feed is to notify you of a new post or reply. The rss reader will not give you anything above what is already provided on your forum. In other words, you should just use the active topics page of your forum.
I believe the purpose of an RSS feed is to give you the whole article and save you time. I prefer to not use the active topics page. Its much more efficient to just read everything in a gmail conversation or an RSS feed. If I was simply scanning titles to decide what I wanted to read, then, yes active topics is fine. But I read every post.
Back to the original topic, I found that my "check" user (ie. non-admin user I can use to see how forum looks for others) subscription DOES work with gmail conversations. So there's an issue with the admin for some reason. I'm going to examine the headers of the emails.