The delegates.xml file looks interesting, and `convert -list delegate` lists a large number of formats that we don't need to support. I'm not clear on the diff

The delegates.xml file looks interesting, and `convert -list delegate` lists a large number of formats that we don't need to support. I'm not clear on the difference between a "coder" and a "delegate". Do I need to add a policy.xml entry to for each delegate?