There should be some warning and/or prompt to prevent you from deleting a user that has things that they own. We recently deleted a user who left the company; we checked that they didn’t owner anything but later found out that they had created a custom period within a favorite and the favorite stopped working. Support mention that they have seen this issue before.
Same thing for deleting periods, some prompt to say this is being used in XYZ so you can either go and fix them or delete the favorite also.