A mod and a user on my boards want to unregister themselves , if i delete them , they'll NEVER be able to join again ? ( is that so ? )
What i want is ....If in future they want to come back as a mod or as a user , they should be able to do that !
If the mod wants to come back as a mod, he should just leave his account up. There is no real benefit to "unregistering" unless you're paranoid that people will PM you in your absence. Otherwise, deleting them shouldn't prevent them from reregistering in the future, after which time you can mod whomever you like.