That's the thing. Nowhere is it written that there's no changelings in FR and it is very save to say that there can be. I mean, you have everything you need to make them - dopplegangers and humans.
It's safe to say that there can be, but not that there are. See the difference? Until they produce a FR product that actually features changelings, we won't know for sure if there are canon changelings there...and, yeah, some people are really fussy about canon. Moreso for the Realms than for most settings, I've noticed.
How to illustrate this? How about this: it's very safe to say that there COULD be lightsabers and Jedi in the Star Trek universe. It's a whole universe, after all. Even if they're not called exactly the same thing, there could definitely be brown-robed mystics with telekinetic powers and light swords.
There could be, sure--but it's going to drive a lot of Star Trek purists nuts if you try to bring one into a Star Trek game.
Some people would just say, "Hey, cool! My Klingon wants a lightsaber now!" Others are going to say, "I want Star Trek that sticks as close to the source material as possible, and we've never seen lightsabers in Star Trek."
There's nothing wrong with either way, but it's a bit dickish, IMO, for EITHER perspective to crap on the other. Telling the Trek purist that he's wrong and silly for not wanting lightsabers is as bad as the Trek purist telling a different group that they're wrong and silly for playing with Vulcans and lightsabers and having a good time doing it.
InnaBinder made a request with certain parameters. Sure, it would've been nice if he'd been a little clearer about those parameters in the first post, and to be honest, I think they're still a little unclear--"not setting specific" is really tough to demarcate, given that about ninety percent of what's in the books has SOME connection to SOME setting. (Is Radiant Servant of Pelor setting specific? Seeker of the Misty Isle?) Without knowing exactly where the line's drawn, it's gonna be tough to figure out what is and isn't fair game.
But he's made it clear that he doesn't think FR-specific stuff and changelings should mix, whatever the setting is, so let's just let it lie at that.