A recent Facebook post reminded me of the old days of fandom roleplaying and fan fiction, when everyone had to post prominent legal disclaimers to avoid being sued by a favorite author, and even that didn't prevent threats and harassment. As a writer myself, it's not hard to understand the kneejerk reaction: these people are stealing the work I spent years developing, then years more jumping through the hoops of publishers and agents ... but the majority of these fandom folk were simply expressing their joy and devotion, not claiming the author's words as their own.
Over time, the attitude towards fandom softened, but it is still ridiculed, derided and given side-eye by many. I missed many of the horror stories, but I was present for the Anne McCaffrey's "Renewable Airforce" drama, when she set down the sexual orientations for the riders of the various colors. Within her rights to do so, perhaps: at the time, it was unequivocally "her world, her rules." Some will argue that since it couldn't be interpreted from the books themselves, fans were free to interpret as they would, as long as they didn't claim it was her stance. Regardless, a lot of the fandom games I played in scrambled, rewriting old characters and old plots, sometimes scrapping them entirely, to retroactively work with these rules.
On a lighter note, I'm put in mind of stories of fanfiction writers who had written Luke / Leia romance stories after the first Star Wars movie, and then the frantic scrambling at the revelations later. I've heard there's even an official novelization that at least hinted at a romance there.
A small group of friends and I approached Gayle Greeno, writer of the Ghatti books - telepathic cat companions - to ask if we could create a small fandom game in her setting. She was confused and a bit tentative about the idea, but approved it. Nowadays, it's hard to imagine any author not being familiar with the concept. So of course, especially since I had my own fandom days, I turned it over myself.
When I roleplayed in fandom, it was always in the author's world, but not with his / her characters. Either the fandom was set in a different time era - long before or long after the author's characters lived - or sometimes in an alternate reality, where they never existed. As much as author-insert characters get a bad rap (look up "Mary Sue" sometime), I think everyone put some aspect(s) of themselves into their roleplaying characters. In a world that wasn't ours, that person or people we portrayed was our gateway, our own private vehicle.
For me, my characters were very personal. Sometimes, people would ask friends to "puppet" (temporarily portray) their character for live online events they couldn't make. I could never make myself do this, and I pretty much panicked the few times I was asked. I couldn't possibly. Those were their characters. That went doubly for the author's characters.
So when it comes to the possibility of fandom set in one of my books, I think my reaction would be that I'd be honored that anyone enjoyed my settings enough to spend time in them - as long as, of course, they're not making profit off it. I don't even think I would mind if they were doing unconventional things with the setting. But when it comes to the characters, I'm highly uncomfortable about the idea of someone else writing them. It feels a bit like a violation of privacy. I would never harass, threaten or pursue legal action, but I hope that readers would respect this; or if they chose not to, that they would keep their writings private or for select friends, where I couldn't happen across them accidentally.
So maybe this seems unfair of me or high-handed, but it's my gut feeling, and I can't really alter that sense of wrongness. I'm certainly not a hypocrite; I would never write another author's characters, and I feel that's as polite as not letting myself into their houses, even if all I'm going to do is admire the wallpaper. And I would humbly hope that, if readers knew my stance on this, that would grant me the same courtesy. That's all I can ask.