Very sorry for any wasted time anyone spent thinking about my little problem here, because I just realized it was, once again, entirely my own fault.
Turns out it was an artifact of some changes I myself made to my build's collada import process, way back in 2011, for the purpose of fixing a problem related to playing animations on imported collada figures. The problem stemmed from the way stock Torque "fixes" handedness on incoming collada models.
I say "fixes", because the stock method is simply to rotate the figure from Y up to Z up, without changing the actual left/right handedness of the nodes. Sorry I can't explain it better right now but the end result was that if I had a bunch of animations made for a right handed Torque character, and then I brought in a left handed Collada model with the exact same bone structure, I would expect to be able to play my anims on this collada model, but they did not work as expected.
My hackish attempt to fix it involved flipping handedness on all the nodes individually, instead of just rotating the model, and it worked at the time for my limited application, but clearly it is puking its guts out on these makehuman/blender models.
No idea why it took me so long to think of trying a stock Torque build (doh!), but the idea *finally* occurred to me, and sure enough:
So, anyway, some work to do on my end sorting out whether it's possible to fix my original problem without causing this other problem, but at least the issue is resolved, and nobody but me needs to worry about it.
Thanks for all the hand holding anyway!