The number of places where we have to catch this bug is high enough -- I've already lost count -- that I wonder whether we should be using a lineExp more like `/#[^#]/` to guarantee that lineExp never matches a block comment.  We could have some logic in _createBlockExpressions() to detect these tricky prefix cases and auto-generate such a regexp.

Edit: I guess the regexp might need to be a little trickier, e.g. `/#($|[^#]|.[^#])/` to account for cases like #+eol and ## without a 3rd #... but it still seems possibly auto-generatable...