When someone leaves HCoop and you want to squelch all of his domains and DomTool privileges, run:
domtool-rmuser $USER
This does a few things:
Delete $DOMTOOL/keys/$USER.
Delete $DOMTOOL/certs/$USER.pem.
Run domtool-admin rmuser $USER, which:
Removes all DomTool privileges for $USER.
Deletes all domains to which only $USER has the domain permission. This includes removing all configuration related to those domains in real daemons.