I agree that it would make sense for the more🮦 button to only show where it's usable, but maybe there's a reason that it's easier or more efficient to still show it even where it's not usable.

I've never heard of a way to receive notifications for a thread you don't have a post in.  If they don't already have the feature, I doubt KA will put any effort into creating it -- there are other changes that should (IMO) be higher priority.
I'll keep watching this thread to see if anyone has more information :-)
~ Janice (a KA user)