In my experience, and from what I asked a few friends about: We have never seen an actual "NSFW" avatar in our combined hundreds of hours of playtime, and those that use the avatars that comes close to being NSFW are usually the younger audience. It is possible to filter out avatars from the world space, and only be able to see your friends avatars. Making your own instances (servers), you are able to kick out players that misbehave.
But I would like a NSFW-tag on content.
And as a side-note: The game is free everywhere, Steam, too.
As someone who makes quite a few avatars for myself and friends, there is a flag for NSFW when publishing your avatars to VRChat's servers as well as ones for realistic violence, gore and such. I'm unaware of what impact these flags have for the use of said avatars though.
I have tested a fully SFW avatar with the NSFW flag checked in the past and I was able to use it just fine inside private and public lobbies so what we actually need here is a way for either world creators and/or lobby visibility settings to restrict what avatar flags are allowed within the current session of that lobby, as well as the ability for users to auto hide/show avatars with specific flags checked.
This wont be bullet proof as this relies heavily on user based trust (which VRChat have a long history of being against) and someone can very easily reverse what I did and mark a heavily NSFW avatar as SFWto bypass such filters, but it will be a good start for limiting exposure to these avatars.
I am just a regular (free-)user in VRChat, and have never seen a "NSFW"-tag or any kind of rating on avatars, so I thought there were no such thing. I wonder how it is used then.
But I would like a NSFW-tag on content.
And as a side-note: The game is free everywhere, Steam, too.