These are some of the features I'd like to see in an RSS reader (I've actually considered trying to learn to program just to build a reader that has these features):

* Import a list of feeds from a simple text file. I find it strange readers don't support this. If I have a list of 50 rss feeds, I don't really want to enter them one by one. Importing from a file another reader has exported is great, but I'd like to import from a text file too.

* Filters. Per-feed and per-category. Again, perhaps naively, I imagine this would be simple to implement but I don't know of a web-based reader that does this and I usually have to resort to Yahoo Pipes or similar, which is a pretty clunky solution. Filters like: Only show entries containing "bar", or don't show entries containing "foo". Bonus points if I can edit a multi-line list of filters, so if I want to filter for 50 separate words I don't have to enter them one-by-one

* Sort-by-newest that works properly across categories. I currently use feedly and somehow in category view posts 12 hours old show up ahead of posts 3 minutes old.