I discovered a bug! I want channels to only be created by admins with studio access, each one attached to a label. That way it's possible to limit use of channels to spots where we have added a "Labels" field. I have turned off the "Create Channel Auto" permission for all levels. It works for most instances of hashtags being used on the site, people can use a hashtag but there will be no auto channel created.

BUT - if someone uses a hashtag in a profile field, it will still automatically create a channel. I was able to repeat the bug on my test account.