Another editor-based solution: text "rectangles" in Emacs.
Highlight the code you want to comment out, then C-x-r-t #
To un-comment the code: highlight, then C-x-r-k
I use this all-day, every day. (Assigned to hot-keys, of course.)
This and powerful regex search/replace is the reason I tolerate Emacs's other "eccentricities".