I have trained with people whose elbows could bend more than 10 degrees backwards. That is a really 'icky' feeling because when you apply a lock, the elbow goes past the point where an average elbow joint would have broken and it just feels wrong.
I love training with the ultra flexible double jointed people. Particularly use that training to find where they should go that way you are already there and ahead of them when they make their move. Definitely some thing that could help in the real world when you are surprised! To relate a story with this I was teaching at a seminar a couple of years ago and just picking random people to show the techniques on. One kid was uber flexible and of course double jointed. I did not know that but when he adapted to what I was doing and moved to another place I could feel it before he went there and walla I was already waiting and the trap/lock was put in place so while it changed what I was showing it also showed everyone to be flexible in your approach to locks and roll with the flow and keep ahead of the game. So it may feel wrong but do not stop or freeze just roll to the next area/movement and let the next thing happen. You of course already know this so I am just relating for other peoples benefit!