You can't flag a post if you don't have enough karma. What the threshold is gets tuned periodically, but I seem to remember that you get a lot of features at 5

You can't flag a post if you don't have enough karma. What the threshold is gets tuned periodically, but I seem to remember that you get a lot of features at 500 karma; nanch currently has 409 karma, so I wouldn't be surprised if he can't flag it.