The original motivation for this change is trying to fix#560 where the comment was attached to the JSXText node instead of the JSXExpressionContainer because it used the globalPrecedingNode. In general, I don't think that it is very safe to attach a comment to a random node just because it happened to be before.
I tried to delete the globalPrecedingNode codepath and I think that it actually improves the results. I'll add inline comments in the pull request to explain the various changes.
Fixes#560
3b66af3d60