\\ for? Help finds nothing on it. An odd number of backslashes greater than one are grouped by two and the last one is displayed with a different color. This indicates that it should mean something.
There also is a (connected?) little bug in the frontend (Mma 8.0, W7). When a text what is ended by the odd number of backslashes is commented with
/, pressing the combination again leads not to uncommenting, but to further commenting like this:
a\\\ (*a\\\*) (*(*a\\\*)*) (*(*(*a\\\*)*)*)