Response received:
In any event, I can ask tech to run a cleanup script that can (but does not always) temporarily correct this pagination error. BUT, bear in mind that this is an issue of appearance only; there won't be any actual posts missing from anyone's view -- rather, it will appear as though there is another page in a thread that you can't get to. Don't fret -- that is a phantom page and there isn't really anything there.
So it seems that probably the most effective way to deal with the phantom pages is to post something, as you have been doing, and live with it.