I have in my editor ( NEdit) a very convenient macro : I select any number of lines then hit Alt+q, and the whole selection is commented out. I select any number of commented lines (or not, it doesn't matter actually) and hit Shift+Alt+q and the selection is uncommented.
I think such macros are extremely easy to program with any serious editor, and even comes included in many. That makes multi-line comments of little interest IMO.