> 
> The grave accent is positioned on top of a vowel.  

True.

> It looks
> just like a back-tick, but has a very different meaning.  It
> means "this is pronounced differently".  English has no
> particular use for this form, so we tend to be sloppy and
> confuse it with the back-tick (which stands in isolation).
> 
> Or, at least, that's my reading of the situation.
> 

Well, I am having trouble proving this...  :) but what I *think*
is correct is:

1. The word "back-tick" is pure slang.
2. The symbol in question was originally used on equipment
(typewriters, hardcopy terminals) capable of backspacing and
reprinting, e.g:  letter e, backspace, grave accent.
3. This almost becomes a semantic argument. Yes, we don't "use" 
it as a grave accent, but I still think that is what it "is." As a crude
analogy, Ruby's inheritance operator (<) really "is" a less-than 
sign, but is not "used" that way.

My research is ongoing... :) :)

Hal