It might. Then again, it may be an indented natural that's been there forever.

I think a diamond with a natural that you can feel with your fingernail would still be considered a crack. JMHO

Good decision. When I read your initial post, I was going to write that it sounds like the stone may have a "cavity"... If so, or something similar, an inside feather (codeword for fracture) connecting to the surface is bad, bad, bad. Your stone is more than at risk for cracking; already it IS cracked to the surface.

If it had been a natural (portion of the original rough surface left) or nick (small, shallow notch on facet junction) on or near the girdle, it probably would have been fine (and limited to just the surface). I would not describe either of these blemishes as a "crack." For what it is worth, and since it is mentioned in this thread title, a "chip" in diamonds is usually rounded and relatively shallow, and occurs on a facet junction. It is usually the result of damage to the surface either during cutting or wearing.