I realize there are nuances and subtleties that separate these tags, but their meanings are so similar in the context of tagging an image that there doesn't seem to be a reason to keep them all separate. If the defining feature of public_nudity is the fact the participant is fully nude (at least enough for the nude tag) then exhibitionism + nude would accomplish the same thing. The difference between public_nudity and exhibitionism often comes down to some context not present in the image (or maybe willingness which would make exhibitionism comparable to rape in that sense). My main issue with how exhibitionism is defined is this part:
Often the participant is willing and makes an overt effort to gain the attention of onlookers.
In a large number of images tagged with it there are probably no onlookers (post #1432072 post #1482941 pool #8005) or the subject is actively avoiding being seen by onlookers (post #1700109 post #1682819) Though this one is more rare since it clearly goes against the main idea of the tag. I realize that sentence is mostly just a guideline and not a hard requirement. But without that part, the definition is essentially identical to public nudity's definition.
This issue seems to have already been touched upon in forum #28265 though that topic didn't seem to come to any real conclusion.
On that topic, public an ambiguous tag if it's meant to refer to any kind of sexual behavior in a public place. Under current definitions, someone who is simply nude (in a completely non-sexual situation) in a public area wouldn't be tagged with public but it would be tagged with public_nudity (and possibly exhibitionism as well depending on context that may or may not be present in the image). Which is fine if everyone's okay with public being ambiguous in that way.
A lot of images under public_nudity are pretty much just nude + outdoors. If the setting is just a beach or a grassy field with no other (unexposed) people around (i.e. post #1470151 post #1024373 post #208057 or post #636311) then it shouldn't really be tagged public nudity, right?
I'm pretty much rambling here, but I just wanted to put these thoughts out there.
Basically the bottom line is that these tags need some cleanup (which I'd be happy to do) and I wanted to make sure I have the definitions straight before getting to it (and in the process, dispel any misconceptions I or anyone else may have about these tags). I apologize for my incoherent writing.
p.s. on a slightly related note, zenra has a very similar meaning to pool #1536 (casual nudity) though the two aren't quite the same thing. Should the tag be done away with because of the pool's existence, or should I go through the images in the pool and tag zenra where appropriate. The wiki is pretty vague about how the tag is to be used or what really sets it apart from the casual nudity pool.
Updated by Tom23