I'll defer to Omega on this one too, but I've heard Bas Ruten say basically the same thing during Pride contests.
One of my fellow bjj whitebelts who has done some shootfighting made a comment yesterday I'm not sold on. I wasn't able to ask my instructor as a number of us were on our way to our cars when it came up.
What the guy said was that achilles locks are not usually going to ever cause real damage, most of the time you don't have proper leverage. This is why, he said, you usually don't ever see anyone tap to one and you see people switch to heelhooks. Is this accurate?
If somebody gets me in training in a simple Achilles pull, and I am in a period just before a fight, I tap. Why go into a fight injured? But hear me when I say that on that same Achilles pull, I will never tap during a fight. This is a move that just hurts; it doesn't break anything and is easy to defend. I'm talking about the straight Achilles pull here, not when he brings your leg over to the other side.