A qualifier is an identifier that groups a person into an appropriate demographic. Location could be a qualifier (for a local school or sports team community for eg) or it could be a more specific action that people take to demonstrate strong interest in a subject (eg: sign up to receive a newsletter, follow social media). The more qualifier groups a person falls into, the stronger their likelihood to become an engaged community member.
To take your examples:
Being a man, liking comic books, and living in Colorado are all qualifiers.
Following on social media, or signing up for emails are further qualifiers.
Does that make sense?