There are 3 stalls in the office ladies room. If the extreme left and right stalls are occupied and I hear someone doing #2, is it OK to use the middle stall? I usually walk out and return 10 minutes later. Is there an unwritten rule for this?

"is it OK to use the middle stall?" Why wouldn't it be? If you don't like to do so, your returning later seems a reasonable action, but what if you reee-aallllly have to go?

What do you do if someone is having a bowel movement in the middle stall and both left and right are free? Do you walk out and leave two perfectly good toilets until you can have a wide enough 'grace space'?

There is no rule, written or unwritten that declares the middle stall a buffer zone. If it was, it would not include a toilet.

Precisely the point ^__^this is a cool post

if you gotta go you gotta go, i wouldnt wait...but its so uncomfortable to be in there when thats happening...i wish they were sound proof haha

Unless you are uncomfortable being in the restroom while someone else is having a bowel movement then, by all means, leave and return a few minutes later. It is understood that public restrooms are meant to be used and certain things will, of course, occur from time to time. The only "rules" are the same as those for any public place which, basically, boil down to "Remember you aren't alone." Otherwise, do what you have to do, wash your hands and continue with your day.