) In regards to ripping out beating hearts, that would **not** be safe because it'd get one of the dark tags (which are also mutually exclusive to safe).
I agree that the sheaths/balls thing doesn't belong in the Safe tag. I was going to suggest a rewrite that would make it make more sense - that is, replacing @"not detailed (eg. covered in fur)"@ with @"nondescript bulges (eg. hidden by fur)."@ And I get what the "@just happens to be present"@ thing was trying to imply in terms of ferals that just kinda have the silhouette of a sheath slightly visible..._
...*but the problem_* with all of that is that it might as well just be lumped in with "bulges" and therefore should be considered Suggestive instead.
As far as the exception for PG-13 media, well, it's an _*exception_*, isn't it? The MPAA isn't exactly consistent about what they deem acceptable, either, so I wouldn't count on the entire body of work on IMDB to dictate what a furry site deems sexy.
As for the rest...I really don't have a problem with the rules as written. I think in the future, once we've got this nailed down, having a visual guide (sorta like a comic or something) to go along with each rating tag could help people make better sense of what belongs in each rating, but we'll cross that bridge when we come to it.