I think our major problem is that everyone has a different idea for what constitutes a post being "safe" vs "explicit". Moreover Albert and Hazuki (who seem to be rallying the most vocal viewpoints) have conceptions that are entirely incompatible.
Albert as of late has been arguing for "safe" being something very close to SFW (with the proviso that looking at anime girls at work is never going to be a good plan). He relegates lingere and skimpy swimwear to questionable regardless of innuendo. This is a more conservative stance than I remember "safe" ever being treated prior to the advent of Safeboru, and leads to all sorts of subjective assessments to be needed to made without any real objective guidelines. As we have discussed in other threads, subjective decisions without hard and fast criteria are never going to be in agreement across the userbase and will lead to disputes.
Hazuki has been arguing starting from forum #19183 for something in the opposite direction where even tasteful full-frontal nudity is treated "safe". While I can buy the argument that mature people can and should treat nudity devoid of sexual intent differently than pornography, I certainly wouldn't want to come across post #571727 if I was browsing Safebooru with friends or family about.
Albert throws the "simpler metric" up above as a straw man's argument, but in my experience, it's by and large exactly what we have been doing forever. An abbreviated version of howto:rate. The two things to point out of the way he worded it though are that he de-emphasizes the exclusion of "implied sex", and (incorrectly in my opinion) makes it out as to say that judgment calls of tastefulness or sexiness are no longer needed.
Rather those two points are what allow the absurd cases to be handled appropriately. "Implied sex" or innuendo is a very broad brush that can be used to exclude fully clothed subjects with obvious sexual intent or content and requires the poster to take sexiness and tastefulness into consideration.
On the other hand, I wouldn't call lingerie or bikinis or even fully covered non-sexualized nudity as "absurd cases" of rating "safe". If you can see it on a Victoria's Secret ad at the mall or at the beach, or broadcast TV, or anywhere else kids regularly frequent, it obviously can't be all that bad. The sticky point here would be museums displaying full frontal nudity, but that's a place I think where it's the venue that makes it acceptable.
I guess basically my point is that I don't really see what is wrong with the mostly objective system we have been using and have mostly codified in howto:rate.
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