tl;dr version:
FOR ALL USER'S SAKE please use PMXEditor to do a PMX check by selecting File --> Validate PMX model (the bottom-most option) and fix the errors reported there before shipping out your edits, so that you don't induce your users with pains in the neck. Especially display-related issues, pretty much everyone fails at that
Full version:
Almost every time, when one uses an edit from dA, he'll inevitably find out there are always problems - after all, nothing can be free of bugs. Serious issues include mis-rigs or rigidbody set-up failure which makes stuff look terrible, but there are also some more subtle ones that most people