One letter increments wouldn’t work because each commit has to leave the program correct. For example committing the first f of a for loop would leave the code with a syntax error. But you often should break up changes into as small as possible commits that leave the code correct. E.g. make one commit that refactors the code (no change in program output), then another change which implements the change in program behavior that motivated the refactor. This generally makes commits easier to review, less likely to contain defects, and easier to attribute bugs and roll back.

I forgot who coined the expression but it's a good rule "first make the change easy, then make the change", my top recommendation for incremental changes.

Just a tiny modification and it would work - do one letter increments only for comments