As for now at least, all operations on reputation are addition-based and therefore commutative: their order doesn't matter, and undoing an operation returns your reputation to the previous state.

With this 1% rule, however, it breaks down. For example, if you downvote someone when you have 1000 reputation points, and then undo the downvote and downvote him again when you have 10,000, it means that you'll lose 9 points for nothing.