Well, here's what I've gathered from closer inspection.
I opened up my remote and compared it to the photos of the rh1 found here:
http://www003.upp.so-net.ne.jp/doggie/linu-zau/rem/rem.htmThey are virtually identical. The only noticable difference is an extra resistor between L1 and R3 (see left photo at the above link) and a tracer or two. Here is a photo (sorry it is so blurry. I couldn't get my crappy digital camera to focus on it.)
http://dave.maddockfamily.com/zaurus/remote.jpgSo, I checked out your hypothesis. You are indeed correct, the ground and key lines have been changed around. I tested this by inserting the remote jack 3/4 of the way in in both factory-default and swapped wiring configuration. In the first case, nothing, in the second I got audio, which indicates to me that the RH2 has the ground wired to the sheath and not the first ring.
However, swapping them does not make the remote work. With the remote's plug 'fixed' and plugged in properly, you get no audio and no response when pressing the buttons. I tested the buttons using the keyhelper settings program. It wasn't catching any keycodes.
Frankly, I think Sharp simply wants to screw over its customers who are upgrading by forcing them to purchase a new remote for no logical reason. The product is virtually identical and it appears that what changes do exist are there simply to force incompatibility.
Needless to say, I'm now in the market for an RH1. Anyone got one lying around?
Dave.