For a little while I have been enforcing this rule.
I want to clarify that purposely trapping people inside dispensers
in the nether spawn is not allowed.
You will be asked politely to remove the constructions.
If you choose not to listen you will be kicked. If you return
and continue like a dummie you'll be banned for about 1 hour.
It's a really really cheap way to get kills, people should have fun
and not be insta-killed when going in the portal!
If you place sentries in the nether, atleast make it so there is a
chance of someone to destroy it.
also, Going Spy won't help. You'll
get stuck in the dispenser and recieve a wrench to the face