I never really get how this works: since 'a friend' can pick up or 'share' an entry or comment with other friends, so that you can comment on the entry, even if it doesn't originate with your 'friend' - only their sharing of an unshared friend, so to speak. That would be fine if the entry then became the property of the friend sharing, but apparently not.
Anyway I was firing off a few home truths about certain artists, that clearly the unshared friend (the originator of the entry) didn't appreciate - or more likely - a couple of other contributing commenters clearly didn't agree with (not my friends, nor I theirs) and I ended up getting barred from the thread - although informed on their responses. I'm used to this happening on blogs, and it's worth it to wind up a few snotty critics and their retinue, but on FB basically I'm baffled as to who holds the authority in these cases. The friend that 'shared' this item clearly hasn't de-friended me - as far as I can see - and since my comments were explicitly addressed to them on the thread - I fail to see why someone else gets to choose.
I use a different tag on FB and mostly as a platform for political rants - where things are much livelier and yet more tolerant! - so this is not a big deal really. Just saying...