I'm not against local variables for counting called i and j.

I'm against a big list of forward declarations, with tens of different variables, each with a very short name, and a comment explaining what this is an abbreviation for. Just replace the names with the comments, with underscores for spaces, using find and replace. two minute job for the whole code base, much more readable code almost everywhere.

I agree that functional languages may be a counter case; but codebases in C and python (in my experience), benefit greatly from well named variables.