It would discourage the player or a given IP from the server. It could be developed more, to have sub commands:
./discourager [add] [player]
./discourager [del] [player]
./discourager [list]
Some ideas:
-> Random lag spikes with other player position packets being sent to them.
-> Random freezing of the player every now and then (for less than half a second so it is noticeable but just looks glitchy).
-> Probability when they type a message that it doesn't send to the server.
-> Random Thread.Sleep when receiving messages.
-> Every few blocks will re-appear when placing them, and when destroying.
-> And obviously, randomly disconnects them from the server every few minutes (5 - 15 minutes maybe?).
This would be an effective command and against annoying players that persist in breaking the rules. When /tempban just doesn't do a good job, you can really get to them by making them suffer.