I got an email about this very unusual (and dangerous!) Achille's heel piercing:

Hi Elayne, My name is Chris. I just had a question for you and would like your input.  I just got my ankle pierced between the ankle bones and the achille's tendon. I've had it in for two weeks and its a 14 gauge PTFE. The piercing is great and everybody either thinks I'm crazy or they love it. It's healing just fine, a little sore but I was expecting that. My question is, do u see any long term damage or and problem with this piercing at all? If you could please email me back I would love your advice. Christopher

My response: Hi Christopher, I'll openly admit to you that this isn't a piercing I would do or recommend. As my book, The Piercing Bible, describes it in the "Risky Piercings" section:

Piercing behind bone, tendon, or other anatomical structure can cause excessive bleeding, nerve damage, and/or loss of function.

So, the risks are pretty serious and certainly should cause you to be very careful with it and to take it out if you experience any loss of function. And, of course, should you leave it in and experience complications, it may be possible that you would be unable to walk, which is a pretty serious dysfunction to risk for 

I imagine you've seen this? http://wiki.bmezine.com/index.php/Achilles_Piercing

And this is an article in which a man stated he had quite a lot of complications as a result of the same piercing.

Please safe!

Elayne