Dieses Problem, dass in den letzten 12 h Flags möglich sind, obwohl Upvotes nicht mehr möglich sind, habe ich gerade hier gelesen:

Fix for End of Payout Period Downvote Abuse

In Hardfork 17, a change was implemented to prevent upvote abuse by creating a twelve-hour “lock out” period at the end of a post’s payout period. During this time, users are no longer allowed to upvote the post, but they can downvote.

This change opened an avenue for abuse, where a user could downvote a post during this period with no opportunity for stakeholders to negate the downvote by adding additional upvotes.

Hardfork 20 will change this “lock out” period to a “cool down.” During the last 12 hours of a post or comment payout period, upvotes and downvotes will still be allowed, but their strength (for the same amount of voting power) will decrease linearly from 100% to 0% over that 12-hour period. In other words, it will take twice as much voting power to have the same impact on a post’s payout if the vote is done with only six hours left on the payout window instead of twelve. A downvote cast in the last minute would have virtually no impact.

This change has not been implemented yet, but we have decided to include it in the hardfork, and are tracking the progress here.