I
believe fade to black is ok, it's just going into actual detail on sex that's the issue.
I'm not sure if simply saying the character is naked and leaving it at that counts though.
If I go to the ruling directly it says:
Use Spoiler Codes to hide risque content.
Iwaku allows roleplays and stories to develop naturally, and that will occasionally include sexual or violent content. When you are posting a scene, story, or image that has questionable content, please use the (spoiler) code to hide it with a content warning. That way people will be prepared. If you are running a roleplay that is purely filled with sexual content, it must be posted in the Libertine Roleplay section.
And if I'm reading that right, there seems to be a difference between 'questionable content' and 'sexual content'.
And since simply being naked, end of story isn't really sexual at all it'd
probably be fine under a spoiler tag.
But then there's this:
When sex scenes happen as a natural part of plot development or progression, you are allowed to do them outside of the Libertine areas. All you need to do is wrap them with the spoiler tags and give a content warning.
Note that this does NOT mean you can do these scenes with members outside of your age group, however. The age group rules still apply.
Which seems to suggest that difference mentioned above is only intended for non-libertine RP's between people in the same age group.
If so, then it's might not be allowed.
The issue here is really what counts as crossing the line is at least somewhat subjective (like there's a ton of obvious don't cross zones, like anything that's actual sex. But at a certain point you hit the "Is mentioning this counting as sexual?).
And ultimately it's based on whatever the law makers wherever the Server is deem to violate sexual content laws.
TL;DR - Maybe, logically speaking simply referencing nudity should be fine. But it's really up whatever the law makers of (insert servers state here) deem inappropriate.
I'd definitely wait for Staff confirmation first though, they work with this stuff often would have been trained/briefed on the specifics.
+I don't partake in any libertine RP's (or any non-libertine that even get's close to mature content) atm, so this is a lot of guess work with the rule's wording.