I had a thought: Ratings can be treated like tags, right? rating:e, rating:q, rating:s. Might it be possible to reduce work on rating changes by setting up implications that automatically change the rating to Explicit if it contains anything that fits its description?
exposed lower genitals (penis, pussy etc.), sex acts, high amounts of violence/gore, or various body fluids. Scat and watersports, which commonly fall under extreme sexual fetishes, are always tagged as explicit.
Would a rating tag added to the tags change the rating accordingly? Just a thought. Of course, if we had complex arguments for implications, we could do the same with Questionable and Safe, but there is otherwise nothing else we can do on that front. At the very least, this would make things easier.
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