I'm sure most RPF consumers have a good 'this is not really real' filter working, though I think you're more likely to run across people with slender grasps of reality in fandom than elsewhere (based on my extensive experience, not a wildass slam), but I think it's also that RPF consumers/producers may have more unexamined assumptions that doesn't lead them to reminding themselves before writing and/or reading that they are concerning themselves with the not-real activities of real people.

may have more unexamined assumptions

Such as what?

I think there are insane, bad RPF writers out there; just as there are insane, bad gen, het, and slash plain-old-fic writers out there. But I know there are at least a *bunch* of actually-very-clever people who write with the attitude that RPF is media subversion and their opportunity to take an authorial hand to the hegemonically-controlled pop-culture 'scape presented to them.

IJS.

I guess I plain old don't see the subversiveness. And I'm quite uninterested in hypothetical celebrity.

As a wish-fulfillment, as a manipulation, I can see the urge to write. Some. I just don't have the urge to consume.

I'm amusing myself by contemplating Viggo's neighbors in New Zealand chatting to each other about that nice young man down the hall who carries a sword around.

Well, for one 'the past is a different country' -- sf fans who read alternative history are often well-versed in actual history details and get lots of pleasure from picking out where the author has included such details accurately and where they're deliberately departing from the verifiable historical record. But there's also the understanding that if you get into the head of, say, Teddy Roosevelt in 1906, you're dealing with a worldview that basically makes many different assumptions about the world and how it is. He's not a 2002 guy in 1906 clothing, he's a 2002 conception of what a 1906 guy would have thought and felt and acted.

What I think I'm struggling to say is that with historical fiction and alternative speculative fiction -- besides the imprimatur of it being professionally edited and published -- there is a tacit acknowledgement of recognized artifice. Lots of fnords between the lines to show that this is speculation based on real details and people.

Do you consider The Alienist alternative history, Theodosia? In my head there's a range of historical RPF that moves from shoddy biography to Jean Plaidy through The Alienist to (damn, I'm blocking on any examples) what I'd consider alternative history.

edit: And I'd be worried if puppyslash readers had no fnords.

I'm not sure that the author considers it alternative history, but I certainly do.

True enough (edit: re historical/alternate fiction). My whimsies about Viggo are just my conceptions of him as modified through seeing the occasional interview. Contemplating him and Orlando getting together is even more a flight of fancy. I guess I see actors as being nearly as much a construct as the characters they play. Mentally, they're faces and voices on a screen. If you wanted to get all Twilight Zone, I have no empirical proof that they're real human beings as opposed to being characters in that long-running show some people call Real Life.