I didn't long-press it though. Just a tap.
Let's see, I suppose I'd need to look at koreader/frontend/ui/input.lua to fix it up? (If I find some more time, that is. I probably played around with the device quite enough for today.)
Edit: ah wait, there's also input.c. Yeah, this'll be for another time.
Edit 2 (many hours later, after I found some more spare time): Okay, I got it all working splendidly with only a few small LUA changes. I'll stick it up on Github shortly.
Edit 3: for those who can't wait,
try these changes (only the one in frontend/ui/input.lua is really necessary).