@algernon @oblomov this aligns closely with my experience
So far I don't block on the absence of those specific headers because I want RSS readers to be able to get through. For the most part they should mainly be fetching the feed URL and maybe the site's favicon, but there are exceptions as you noted.
Some reader software will fetch arbitrary pages (at the user's request) and check for the existence of a <link rel="alternate"> tag. Since I strongly encourage readers to follow via RSS I'd hate to ban them when they try to do so π