http://schismtracker.org/hg/rev/eb3ebf65161e
This behavior was observed in registered copies of IT.EXE (the same copy that has shift-chording in the pattern editor)
Did implementing this IT.EXE bug bother anyone?
That seems like awfully specific behavior for a bug... but then again, I also can't come up with any reason why it might have been deliberately implemented. I can't think of any reasonable purpose that particular combination of actions might serve. Either way, it makes it pretty hard to enter a chord with a G# in it.