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This is currently the preferred way to get a license back. Disabling a user gives the license back so that another user may be created. There is a known bug that disabling a user will not give back the license due to the user still belonging to a group and or the cache statistics have not been flushedIt is preferred to disable a user as historical information and user history is maintained.
Removing a User
Before a user can be removed all edits, comments and spaces must be removed or the user will not be removed. It is advised to only remove a user, if that user never actually used his or her account.