Celticjim: So has anyone else seen a true case of this bug potentially changing the outcome of a game?
Here’s one:
Open Fast Espionage (drjohnj vs. MTC)

The only winning strategy i can come up with in this game requires making use of the fact that my opponent’s pieces cannot move back to their previous squares. So if my opponent exploits this bug, I cannot win, and now he has done so.

I have reported this as another case of the bug (http://81.91.83.6/en/ReadBug?bgi=1995) and expect either:
1) The bug is fixed immediately and the illegal move reverted (unlikely but best option) or
2) The game is ended as a win for me due to my opponent’s illegal move (could be considered unfair on my opponent but I see this has been done before…).