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The recent spate of V:tR questions from a new user has brought the mess of WoD tags to my attention. (And I do like cleaning up messy tag clusters.)
According to its tag wiki, world-of-darkness is only for asking about the setting:
The [world-of-darkness] tag should be used for questions concerning the setting of White Wolf's supernatural games. For questions concerning the mechanics, use [storyteller-system] for oWoD/cWoD games and [storytelling-system] for nWoD ones.
It's being habitually put on every question about a White Wolf WoD game, though, which results in tag soup like world-of-darkness vampire-the-requiem nwod storytelling-system. Clearly there is a degree of redundancy here that is contrary to the tagging system's purpose.
To add to the mess, I have no idea where the consensus for using world-of-darkness for only setting questions came from. Messier still, it's the synonym for wod, which people use as a system tag instead of a setting tag.
storytelling-system and storyteller-system are supposed to be used for rules questions, but instead we get nwod and wod (which synonyms to world-of-darkness) used for rules questions. Obviously our stated use for these tags isn't how users actually tag naturally: do we synonym away the "xwod" tags to their respective storytell(er|ing)-system tags, or do we go with the flow (and the SEO) and use the nWoD and WoD tags? (Actually, synonyming them to the systems might be a clever thing: "owod" and "nwod" are easier to remember than whether it's an -ing or an -er for nwod/owod, making proper system-tagging happen more automatically.)
Is nwod for only setting Qs too? Or is it a system tag? It doesn't say in its tag wiki, but because it's the complement of wod (which synonyms to world-of-darkness) it's implied that it's for only setting questions by our tag structure. Unless the tag wiki for world-of-darkness is wrong, of course.
Do we need to tag a question with storytelling-system when it's already tagged with vampire-the-requiem, or with storyteller-system when it's already tagged with vampire-the-masquerade or any of the other oWoD games? Is it redundant, or useful?
owod and cwod don't exist, even as synonyms. I'm surprised they're not being constantly applied by new users to old/classic WoD questions. Should we make them synonyms of… whatever we decide to do with the rest of the tags?
Previous meta discussions
There's an old discussion about needing to split nWoD and oWoD questions, but it doesn't deal with taxonomy beyond "yes we should have separate tags".
There's an old discussion about the tag hierarchy for WoD tags. It mentions that world-of-darkness was already intended to be for setting Qs, but doesn't say where or when that was decided. It proposes that world-of-darkness be used like we do dungeons-and-dragons as a tag for general Qs that aren't specific to any edition or that do meaningfully span editions, but the tag wiki wasn't changed to reflect that consensus (if it was a consensus), and it's not being used that way now anyway. (i.e., not every dnd-3.5e question also has dungeons-and-dragons on it, but that's what we're seeing with WoD questions and world-of-darkness). So, it's not being used according to its tag wiki nor this discussion's answer.
I don't have a useful opinion on this beyond "the status quo is awful", because I'm not a WoD player and don't have the nuanced familiarity with the various names' relationships to devise a "right" hierarchy, and I don't have the familiarity with the WoD community to judge what sorts of tags will align with how the terms are actually used in the wild. I am an editing junkie though, and we should have our tags set up such that anyone with a reasonable comprehension of a question can use the tag wikis as a reference for fixing the tags on a new question from a user uninitiated in the Ways of the Tag.