is it a copyright issue that won’t allow them to? Or they just don’t feel like kicking the dead horse about? Even so, if you toggle the “Silly” you get picked up by Syri, Anno and Kaede for a small 2 part orgy. That may be a different reason That’s allowed. I’ve been looking around the forums and Wiki, it even claims that Kasyrra was a mortal from the CoC1 world turned demon. There has to be correlation between the 2.
Setting-wise, there's not really any feasible way for things from CoC to get to the CoC2 world. Kasyrra's portal tech explicitly, and purposefully, breaks the rules of CoC, as a big part of CoC was that the demons were unable to find ways to exit Mareth, as it was essentially the final destination for portals, only having in-portals and no out-portals (except for little things like potions to extend life). Taoth, I believe, only gets over because he's a god (and also a trickster god, specifically) and could sneak through one of Kas's portals (probably the first one, the one with Calla). Kas is basically the only one with access to this tech though, and it's impossible for the others to get out of Mareth without it. There's also probably some outside issues that led to these restrictions, but as things are, CoC people can't get to CoC2.
Also, I think I've gotten that Syri, Anno, and Kaede scene without having silly mode on, but like, assuming it requires silly mode, silly mode is explicitly filled with things that "may be stupid, over-the-top, or immersion breaking." So something being in silly mode wouldn't work for adding something else outside of it.
But in all aspect I wouldn’t mind the small Cameos and little event scenes involving the ones that got us into the kinks we have today.
Yeah, references would probably be fine. Apparently an antagonist to Kinu once you free her and Kiyoko is named Raphael, and he specifically uses dialogue ripped straight from the original CoC Raphael, just in a different context to show how weird and creepy he was. He's not the same character, but he's heavily referential, albeit in a manner to tear down the source material.