From what I could see i've lost quite a few missions and did not lose any of my experience or ranking......I don't think there is a penaltly for someone beating you to completion but only if you accept and then do NOT complete in the time allowed.
but the 200 hour timer is not up..... so it looks like something we will have to wait for next round to see....
Maybe but remember when someone completes a mission it automatically disconnects anyone else who was doing that mission and removes it completely from both the mission data base as well as from anyones running processes so basically i think once it is completed it just disappears without penalty to whomever had the mission and didn't complete it.