I've never been very good at introductions...

[Rares]

Nice to meet you, welcome to the forum! Hope you feel very welcome here and enjoy your stay.

As for your questions

Are 4chan-isms appreciated here? e.g., calling people faggots in a loving way, referring to different groups of people as ______fags, etc.

I've seen enough people here do it, especially in the Discord, but I can't speak for everyone. Speaking for myself I don't mind being called a Rarifag.

Is there a comprehensive list of rules?

I thought so, I will attempt to dig for it. Is there anything in particular you had questions about?

How common is it for a tulpa to talk by proxy? Mine might want to say a few things.

Very common! You'll find that there are actually even some threads devoted for this purpose.

Do you happen to have Discord account?