"I don't see how having characters speak to someone who never replies makes the game more immersive. If he's well written then we will identify with him regardless of whether or not he has dialogue."
No, it would be like a movie, and we would take a more passive role, and it would suck, theres enough wannabe-movie games already.
Link being left handed is tradition, if they keep him left handed (and I really hope they do) it would be for no other reason than tradition, because it has no impact in gameplay, but Link not talking is not a tradition, thats not the reason behind it, is the way the dev team let you make the experience more interactive, and the impact on gameplay would be significant, and in bad way.
And besides, he does have the ocasional written dialogue, but only if we can chose it. Take one simple example, Zelda after telling you her dream in Ocarina asks if you believe her or not, the answer doesn't matter at all, you have to eventually believe her because the game has to continue, so it seems the whole question was unnecessary but it wasn't, it lets you decide whether you want Link to be someone who trusts people or not, all Zelda games are filled all around with those insignificant details but their accumulated effect is what makes the game so good.