I would just love for some tags to be automatically denied, as in, unusable. A tag filter, if you will. Idunno how many synonym tags we have, but they have to be a lot, and to be honest, it's just more work to avoid redundancy. We don't need any word other than "breast", for example. And while aliases kinda fix that, it's just stupid to have so many redundant tags just because some people think like a 12-year old and tag "boobies". Other things, like for example, <name>_(artist) tags are just redundant. If the tag is well made, the color itself will tell you whose name that is.
To leave tagging to only the posters is ridiculous. Maybe we just need more users (who know what they're doing) with power to fix tags globally, as in completely exterminate a tag, or change it to another entirely with just one edit.