Q: What's the difference between "Deauthenticate on Discord Leave" and "Revoke Oxide Group on Discord Leave"?
A: Deauthenticate will completely remove the player from the data including oxide group while it's not the case with just oxide group

What is this "data" you refer to ? 

For instance i am running kits on my server.

When someone does /verify and joins my discord, and registers they are then added to an oxide group that allows use of said /kit command. They are able to claim 200 scrap 1x per wipe, from one of the kits. 

How can i make sure that they are not able to just leave discord, come back, re-auth, claim the kit, and so on and so forth ? Is there anyway to stop this? I have it currently not  deauthenticating, only removing them from the oxide group.