I agree, it seemed like a bug to me at the time, and I wouldn't be surprised if it's fixed now. To clarify, it wasn't the actual page's post that was appearing in my feed, but somebody sharing the post on that page. It's somebody who I want to follow, but I'm not interested in seeing half of the things they share. The permanent un-follow thing is legit, like you said.

Another thing I noticed was that basically the same video would be posted by a dozen (and growing) increasingly obscure pages, and my friends (and fb) would share from all the different pages indiscriminately.

If you block one obscure page, another one arrives to take its place within a few days. It almost feels engineered by design, to get around the "never show stuff from this person/page again" mechanism.