But for self voting, I don't know it's probably a serious issue. I think that because you have to split your stake between multiple accounts to do that it will never be as effective as using just one account, so not as bad as self voting. But to really solve it I don't know.
It wouldn't work, if A was not allowed to vote for A, A could vote for B, where B is another account. That would be an endeavor to filter out who's dumping all their Vests on what account, especially if there's a C, D, E, F, and G etc. that a person has.
The point is that if vests are split between accounts they are necessarily small by virtue of being split.