I'm confused now. You're basically just talking about cookies, cache, and other stored identifiers at this point, right?
Yes.
Single-site linkability due to information the user has provided to the website is outside of Tor's threat model. That is what https is for (and also why we ship HTTPS-Everywhere with the Tor Browser Bundle).
Ah, okay that makes sense. I did not know that. Sorry for bothering you in this regard.
Georg