Messages iphone ones that come to top and circle, how unpin; better yet how prevent even happening? I could easily forget it there as does not stack normally looking visually on top others thanks.

Your questions are answered in this Apple Support article for macs and this for iOS, IPADOS except there is no way to turn off pinning a message. However, since you have to intentionally pin it in the first place, then don't pin it.

Ok Joe thanks will save links. I have notes from past, you said I'm inadvertently pinning by holding too long?

Today this morning, a woman messaged me and her message was at top in circle pinned. Now this message was preexisting, been at bottom of 12 message in normal way for few weeks. I have zero recollection of holding anything too long but your pretty sure I pinned it?

Pernicious, not sure how I'm inadvertently pinning.

Ok just tested: hold down, then option comes up bottom un pin/ pin. But today did not do that, she went from unpinned to pin. Did not hold down and select to pin, crazy.

You are holding too long. Think "TAP" not "TOUCH".

Joe, I held down long to see how to do this. I never hold down long, so that was that point. i don't think i pinned it yet it pinned, so mystery, who knows...