When you approach a portal, have it bring up a menu saying “You are about to enter a portal, do you agree to pass through?” Y/N buttons. Preferably this menu would “appear through” any bodies that might be in front of the menu, sort of an “always-top-level” image, if that is possible. If you walk away from the menu without selecting an option, the menu disappears. If they re-approach the portal after saying no or backing away, the y/n prompt will come up again. When the portal closes, all the prompts it generated are closed as well.
Additional option: Make this the default option for accepting portals, and in the options allow the player to disable it if they do not want the menu to appear, & just go through.
To be honest, trollporting is sort of a fun mechanic. I’ve never used it on anyone myself, I have seen it be abused on Piupau(or however you spell her name)… but it does remind me a bit of older games where this type of behavior was common(and worse - you’d get murdered & your gear taken too!) However this seems fairly reasonable for a game like Orbus.