Active Directory database conversion is useful for credentialing users that are not all tied to the same domain, but can make maintenance a pain. The fact that it is not reversible OOTB means to manually revert you will need to perform the following:
1) (have a db backup from before the conversion)
2) Export all changed components since the backup
3) Restore the DB from backup made in (1)
4) Import the components exported in (2)
5) Reconfigure AD groups/roles as needed
An enhancement to the tool would remember AD group/role assignments, and allow re-mapping of AD groups to those roles in the event a reversion is desired. A list and prompt on what to do with unmapped Users could help determine if ready to revert.