This question had a bounty. The grace period expired and the bounty disappeared.
I have a +4 answer there and as far as I know I was supposed to get a half-bounty.
This is not a rant. I know this answer is not worth it, but I am just curious.
It seems that I know the reason.
The answer was posted before the bounty started.
It does not matter when it was upvoted.
Half-bounties are awarded only for answers posted after the bounty starts.