After much discussion internally and with some members of the community we have decided to allow users to change their votes! 

There are a few caveats to this to prevent attacks and to minimize potential abuse of this change, but we strongly believe this change will allow for a higher level of curation and reduce cognitive barriers for content curation. Below is a summary of how we are changing voting:

 - Behavior for new votes remains unchanged.

 - As a general rule of thumb, you can change your vote. The only restriction to this is that you cannot change your vote within the last two hours of a payout if the change would increase the comment payout. This is prevent ninja buffing of a comment at the last second. More on this restriction later...

 - If you change your vote you become ineligible for curation rewards, even on a revote. The idea behind curation rewards is to create incentive for user powered content discovery. Changing votes later does very little to push this agenda, thus those users will be ineligible for curation rewards.

 - Changing your vote still costs voting power. You do not get a refund for lowering your vote, do not pass go, do not collect $200. The user will need to be mindful of this fact because changing a vote that had a lot of voting power with one that is low voting power, even if the weight is higher, might result in fewer rshares awarded to the comment.

 - When a vote is removed, the cashout time of the comment is unchanged. The cashout time is a contract between the blockchain and the users that a comment will not be paid before a certain time. This behavior is necessary to enforce this contract.

 - This should be trivially assumed, but net rshares for a comment are modified as though the previous vote never occurred.

 - Absolute rshares are not changed prior to applying a new vote. This has the effect that vote changing does extend cashout time, but not as significantly as the first vote. We believe this is important to allow new and current voters to accurately curate content as the pending payout fluctuates.

 - In the last two hours before a payout, changing your vote in a way that increases the net rshares of a comment is prohibited. New votes are still allowed as normal. This stipulation prevents a comment from being pumped in a short amount of time without extending the cashout time significantly. This is acceptable for normal voting because a large vote causes a large extension to the cashout time. However, since we do not remove absolute rshares, the extension will be smaller and smaller over time, to the point where users could pump a comment right before the cashout time without having an appreciable effect on the cashout time, effectively creating a review period of 0 seconds. We understand that this change could create an effective review period of 2 hours, but we believe it will be enough of a deterrent to prevent this sort of gaming. Keep in mind that changing a vote that causes a loss in net rshares is still allowed, so there are two hours where votes could be removed or changed to a 100% downvote entirely when the users wishing to game the system could do nothing.