More info found:
It also apparently happens when stickying topics and deleting posts in the internal bbPress forums. In these cases, it sits on the delete URL, but once you manually return to the thread, the effects have taken place.
Some additional information:
I have tested it with Firefox in safe mode and have the same problem.
I tried using other BuddyPress themes, but the same thing happens.
If BuddyPress is disabled, then the problem doesn’t occur.
The problem does not occur if the user that is logging in does not have posting rights.