I have read some of the discussions on meta regarding the "fastest gun" and "tactical voting" problems. As mentioned before, there is a conflict-of-interest here, when you answer a question the temptation to downvote other answers is very high, regardless of whether you comes back later to undo the vote (which now we can't, because the undo grace period is now very short).
It was proposed (and denied) that users who answer a question be forbidden from voting on others. I agree that this is too harsh, but I want to suggest a different strategy:
- Make it more expensive to downvote such answers. Instead of one rep point, it should be around 4 or 5.
- Limit the number of answers that I can down-vote on a thread which I answered to 2 or 3.
This strategy still allows you to down-vote if you think other answers are wrong, it is not as extreme as banning you from downvoting, but it does changes the stakes a bit to encourage a fair behavior.