New setting: save_ignored_users would save ignored users from each run to your config.
Users with downloads that later fail and are caught by the script should probably also be ignored. When downloading a big list at once I have had problems with running into the same "bad" users again and again. This would solve that. If implemented we should maybe think about how we are formatting the ignored_users in the config. Right now they are all on one line which will look bad with a bunch of users.