I'm not convinced by the compound tags. I think it's including data that the medium is not suited for and doesn't really make it any easier to locate individual tags in the list. The fact that Dick Grayson is a character, is Robin I and is also Nightwing III (iirc :/) is information for a wiki. In a tag list it's just superfluous - Robin I will always be Dick Grayson who will always be a character. The tags should be an index not an appendix.
The compound tags do have their uses, for instance we may want 'title: robin' when we need the book rather than the cape, but these should be the exception rather than the rule.
Simple is best. The less complicated the tags are the fewer mistakes are going to be made. After all what are the chances of accidentally creating a new tag by misspelling 'jason todd' compared to 'character: robin ii/red hood/jason todd'?
I think what we really need are obvious tags like 'robin', 'nightwing', 'dick grayson', 'tim drake', and an external system that monitors our tagging and gives us a way to cross-reference them. That way we could look up 'tim drake' + 'dick grayson' when we need the brotherly lovin'! ^_^