I'm told our emergent folksonomy means the attitude toward tags is "don't fix it if it's not broken," and I'm all for letting the garden grow wild until it needs pruning. But looking over our tags history, I can't really tell what constitutes "broken" for tags; what signals a need to curate? Curation, in this case, means starting a meta discussion about intervening to guide the growth of tags or prune back something undesirable. Tools for this include (but probably aren't limited to) synonymising, splitting, burninating, and blacklisting.
I asked on meta.se about this and their answer is that each Stack is independently responsible for deciding when to curate its own tags, without guidance from our Stack Overlords. Since there's some notable confusion about this topic on RPG.SE, it's been suggested that we have a meta post on this site to gain a consensus on what patterns of tag use require active curation in the context of this RPG Stack Exchange and its particular eccentricities.
So, RPG.SE: What are red flags that indicate a tag should be considered for curation? What site behaviour patterns should tell me that a meta question about the tag might be necessary?
To be very clear: I'm not asking for rules about how to curate tags. I'm asking for guidelines to help know when something on the main site means that maybe a tag should get put under the spotlight on meta.