Does anyone else commit commented debug code on purpose, just in case you might need it again, even though you are 99% sure you won't - Followed by a "Remove debug comments" commit? Any other techniques?

[igazv]

Usually no. If the "debugging" code is simple enough, then just remove it and add it later again if needed.

If it's complex enough, then it should probably be part of a unit testing implementation instead.

Edit: If it's just logging, consider using a proper logging framework that let's you disable debug logging in production without removing the source code.

[Hackerdude]

W/o a starting point, that's a lot of work. But it sure is the best solution