It must be a bug. For me, I didn't see the subscribe button at all yesterday, just a plaintext "Subscribe" that I couldn't click. When visiting one of the posts, the button finally appeared today.
datahoarder
Who are we?
We are digital librarians. Among us are represented the various reasons to keep data -- legal requirements, competitive requirements, uncertainty of permanence of cloud services, distaste for transmitting your data externally (e.g. government or corporate espionage), cultural and familial archivists, internet collapse preppers, and people who do it themselves so they're sure it's done right. Everyone has their reasons for curating the data they have decided to keep (either forever or For A Damn Long Time). Along the way we have sought out like-minded individuals to exchange strategies, war stories, and cautionary tales of failures.
We are one. We are legion. And we're trying really hard not to forget.
-- 5-4-3-2-1-bang from this thread
Yes, this is a bug. This has already been reported (https://github.com/LemmyNet/lemmy-ui/issues/1581) and fixed (https://github.com/LemmyNet/lemmy-ui/pull/1661). I assume that after the release of Lemmy 0.18.1 everything will work again as it should.