Pg-13 site but in terms of writing how far is too far?

I know for artists, if they label a link 'Mature content' it's okay to show content slightly higher than pg-13 but what about writing.

I'm just a little confused on the limits. I did review the terms/conditions

Linking okay, but only if it's PG-13. Anything above that isn't allowed to be linked here. If I recall correctly, it's okay to link to a gallery/collection that may include a few mature items, but you can't link to a specific piece that's rated mature.