Re: bp_xprofile_data remains even after user account is deleted.
I doubt it’s a bug but design, deleting an account is a WP process, xprofile data is BP data I would assume that WP is not aware of a plugins tables and therefore couldn’t and wouldn’t delete that data. Generally plugins that create tables do not clean them up if deactivated in case data is still required likewise WP would be in error if it started to delete plugin tables. Of course I might be wrong on all that 
