If you goto "search user's posts" on a user's profile, so it lists all of their posts. If they are on your foe/blocklist it gives you this rather useless display.
Also everytime you click "display this post" it does the search all over again, thus spamming the search function.

A (dumb) solution is to temporarily remove them from the foelist, do the search, then add them back again. eeuuuuggghhh

That is one for the phpBB devs I'm afraid...