It seems on a lot of other SE sites, that sub-tags (like marvel-comics for instance*) are only used when referring to something specific about that sub-tag, if there is no explicit link to Marvel in the question, then it should not exist.
As an example, if I am using the tags correctly:
- Why does theme X appear in marvel comics so often?
- Who is in charge of Marvel comics?
Would use the marvel-comics tag, whereas:
[Question about marvel character]
Would not, as any publisher could own the rights to that character.