It seems all the better self portraits have the camera not being held by the object of the photograph. If another takes the picture, the object can't fairly post it because it wouldn't be his or her work. Discounting timers on the camera, how would one get a properly taken self portrait that would be legal to post?

I think timers would be the best way and are used mostly. I dont know why you would discount them. Any image can be posted here with permission. I think that when you hand your camera to someone and say take this picture of my from this angle here, it is understood that this is to be your photo.