Reddit offers various ways to get feeds that combine content from multiple subreddits. Unfortunately no tags are used in the feeds, but it would be possible to exctract the subreddit name from the post URLs (reddit.com/r/$SUBREDDIT/…) and display it as a tag in NewsBlur.
No, I think the feed will have to publish the category/subreddit as a tag. Otherwise, title filtering is about it.
Okay, I posted a feature request on Reddit.
…and it’s implemented