With the several I have encountered, I've snapped about half of them. Some were so crusted up that even after heat and penetrant, what I thought was the the nut turning, was actually the threaded stem of the latch twisting off.
Try heating the nut and some good penetrant spray (WD-40 makes a new one that has worked for me really well).
If you do snap it off, you have the new one to replace it anyhow.