Let's lay down a few axioms before debating:
- Voting is sacred. It drives our community and is probably the single most important feature of our sites.
- Unvoting, as well as voting, can be misused. Unvoting should not be allowed for everyone IMHO, as is the case of voting. A small degree of chaos might result.
- Unvoting, as well as voting, should be done with care. This goes back to votes being sacred. In order for our content to have any meaning at all, voting should not be done carelessly.
Now that that foundation has been laid, we can examine some finer points, the foremost of which is that everyone learns. My experience may be very different than average because I was extremely ignorant of many things and posted several things during this period. I may have downvoted some answers that were amazing: well explained, and correct. The awesomeness of that content did not change, and if it did, we are free to rescind votes. However, our thoughts do change as we learn and explore. Votes are sacred, and not letting me change my vote is in some ways similar to not letting me vote at all.
Obviously, how this is implemented must be decided with care. The most important thing is that voting should not be done lightly, so this privilege should only be given to those who understand its ramifications and their responsibilities. I propose that we use 5k as the level where this privilege is gained, as it would help bridge the huge gap between 3k and 10k, although that's a completely different debate. Users with 2k rep already sort or have this privileges through editing the answer itself, but I've started running into this problem on other SE sites where I don't have enough rep.
This feature also rarely needs to be used, so a limit of 3 per day or a similar number would probably be in order. The number depends on how much we trust the users.
Sometimes when I've downvoted a post with a comment, the answerer responds with a comment that addresses something I wasn't aware of or didn't know. You guys are probably a lot smarter than me so this happens less, but I feel really bad when I can't undo that downvote
What does the community think? :D