I co-presented a workshop on this one actually... maybe more than once, I don't remember. The time I remember was at TSC in like... 2001?? I don't know, when was the last season of Buffy....
I'm trying to remember what we said were some big areas of shared experience between transgendered folks and multiple folks. Things like:
1. having lots of different names and seeming to change them a lot
2. being considered an extremely rare freak by the medical and psychiatric communities
3. having doctors and therapists think that they know what's wrong with you and how to fix it and that you shouldn't get any say in the matter, by virtue of how you identify
4. what else?
and of course, while the phrase has mostly fallen out of favor in the trans community, many multiple folks are literally a woman trapped in a man's body, or vice versa....