This is an isolated incident. "Irrelevant or Inappropriate" sounds like a euphemism for spam- if Facebook is fighting comment spam then I applaud them. Their algorithm just isn't quite right yet. No story here. "Is this censorship?" Are false positives on a spam filter censorship?
Hi, fb engineer here. This is exactly what's going on. If you recall, there were several articles written a few months back pertaining to comment spam, and very low quality comments (ascii art or 'LOOOOOL!!!') from subscribers. This is part of an effort to curb that and has likely gone awry. It only affects subscriber -> subscribee comments.
What users get up to is a lot less bad than what apps do.
And get rid of the 'like' un-feature. That will go a long way to restoring sanity.