I had noticed this before, and am still trying to figure it out. I have many forums (single simple discussion) set up in Moodle, and I am updating them all for fall. When I use Edit and change the title as well as the post, the new title appears, but the old title is still the same on the breadcrumbs path above:
I had a complaint today about forum changes not being saved, and I wonder if the two are connected. Back in Moodle 1.8 I posted this issue at Moodle.org but got no response. I still find it an odd bug, if that’s what it is. The only workaround seems to be to use the “Update this Forum” button instead of “Edit” at the bottom of the post.
Good tip! Thanks!