I downvoted an answer and explained the reason why in the comments. The person defended his answer with an argument and I decided, that he is right, and I am wrong. I tried to undo my downvote but it doesn't work. It's locked.
I did not even answer the question myself, so this could be an additional test, to prevent tactical voting.
A second addition ...
I initially upvoted an answer, only to realize a few minutes later that it actually didn't answer the OP's question.
So I answered it myself, and wanted NOT TO DOWNVOTE, but to remove my initial upvote.
Because of this provision, I can't.
If this feature intends to prevent tactical downvotes, then please let me retract my upvote.
The idea is that we would always allow you to change your mind, and therefore your vote, except that it could be too easily abused by unscrupulous users.
For example, someone might decide to go downvote all of the competing answers to a question that they've answered to help push their own answer to the top, and then later go back and ...
That means the vote is unupvoted which was upvoted before your answer become community wiki. If the vote, for what you have not earned any reputation, is unupvoted you won't lose any reputation.
After looking at your reputation history, IMO this is the case:
Someone unupvoted for what you earned 10 rep in the past (i.e. when your answer was not CW) ...
Actually the following advice is given by Jeff:
If you feel so strongly that you've made a terrible mistake with your vote, earn 2k rep, edit the post, then change your vote.
Though he does not advice to perform too minor edit. So they know this scenario.
You only have 60 seconds to un-vote on a comment, as stated in this post:
1.You can un-upvote a comment within the first 60 seconds, provided you did not navigate away.
2.Once you un-upvote a comment you can not upvote it again
So this is not a bug in the Android app, it's something that all users regardless of platform, are subject to.
This is functionality the system actually encourages. Consider the two cases where it could be used:
Changing your vote on somebody elses posts.
If you really care about your vote enough to change somebody else's post (hopefully improving it), also possibly giving up your anonymity, then knock yourself out. I've done this myself on posts I've downvoted. If ...
Simple tweak. Lock downvotes only for the users who have answers in this question.
As long as the lock is removed on an edit. To prevent strategic downvoters from editing to fix, you disallow them (them=people who have downvoted and answered on the same post) from editing. Point is, all downvotes should be reversible on edits.
Though I still see problems ...