Sometimes a downvote comes just with an excuse from a person who answered to the same question. I don't want to make a specific example, neither to accuse a specific person, so I'll make an example:
Aanswers the question, there are syntax errors on his questions;
- People make him notice the syntax errors and
Aedits the answer;
Banswers to the question, everything is OK with his answer;
Anotice that he is returning an area of memory which is on the stack, so the code isn't correct, and he downvotes;
- A edits the answer, but downvotes
Btoo, with an excuse like that he is casting the result of
malloc, and that this cast is useless.
So in this case we can't demonstrate that
A downvotes to
B just with an excuse, since there is an appearent reason to his downvote. But if usually
A downvotes for big errors, then he now downvotes for a small error, or for a non-error, a metter of personal taste like casting or not casting the result of malloc. He wouldn't do the same if the answer wasn't competing with him, but no one can demonstate this.
Now -2 points are nothing, but this can happen several times. It may also happen that an user downvotes for wrong reasons, so how do we demonstrate that we are right in that case? Is there a way to debate on the downvote even tough -2 points are nothing? The reason is mainly to be politically correct, not because I care about losing few points.