After doing some testing, it appears the grinding penalty can be completely avoided by simply killing a mob outside the defined grinding area.

To paint a picture...
A player is farming a mob farm for rewards. The player reaches grinding penalty cap and is notified in chat. Player turns around and shoots a zombie outside the newly defined penalty area. The penalty area is completely reset and the player can return to farming the mob farm. Repeat.

I think it would be great if the penalty areas were time-dependent and could be adjusted in the config to define how long the player has to wait before they can earn rewards in this area again.

I considered just adding all new penalty areas to the blacklist.yml, but that would eventually become troublesome as people accidentally trigger penalty areas at their homes, and forever get shouted at for mob grinding when they kill a random mob in the blacklisted area.

Thanks for maintaining this plugin, it's a great plugin :)

This is not a bug, but I agree it would be nice if there is a timer defined for this area as well.

Unfortunately this is very hard to make. I might sound easy, but it is not :-(

This basically the same problem/enhancement mentioned in ticket 449
#449