In psychology, the Other helps us define ourselves. We see other people walking about, and by picking out the things that are different between them and us, we create a more solid picture of who we are. Everybody does it. As long as we aren't jerks about it, this isn't inherently a good or bad thing. But what happens when you recognize so many differences that you feel effectively cut off from the society around you? That's the problem Ai faces in The Left Hand of Darkness as he attempts to reconcile his obvious cultural differences with the Gethenians. It's either that or fail at his mission. And since it took him 17 years to get to Gethen by space travel, failure would be an utter waste of gas money.
Ai's Otherness has less to do with his biology and more to do with his cultural upbringing.
In trying to prevent Otherness, the Commensal system of Orgoreyn actually creates a society based on it.