For some time, I have primarily made posts to Facebook to spread the word about blog posts and documents added to my home server. I rarely used it for anything else. Face book doesn't share its methods for determining inappropriate speech or using their service in ways they don't like, but it is not surprising that posts that used to draw several dozens to hundreds of views (even innocuous ones like telling folks about server maintenance) now only get a handful of views.
Of course, there is no way to prove one has been shadow-banned, but the effect is easy enough to see in my statistics.
I will be searching for other methods of helping people find this blog and the server, but I am strangely pleased to have draw the notice of some pretty big entities and they feel a need to thwart me. Very gratifying!