Thanks for all your advice; I think it's the Motor Control Unit
(Whirlpool P/N 8540540).

If you skip to the bottom of this post, you'll see pictures of the
burned board. Do you concur based on the photos below that it's
the motor control board?

Why didn't the diagnostic test work then?

Anyway, after being totally unsuccessful at getting the Whirlpool duet
sport WFW8410SW washing machine to diagnose anything other than F28
(which is apparently the same "communications error" as the infamous F11
that youtubers all deplore), I finally just took the whole thing apart.

The en133200 F11.126/980-214 EMI Noise Filter near where the power
comes in seemed to be in good shape:
http://i.cubeupload.com/9NouUy.gif

The main computer control board (Whirlpool PN W10063510) also seemed
to be in good shape on the bottom:
http://i.cubeupload.com/3AJpZe.gif

And on the top:
http://i.cubeupload.com/vHyNQx.gif

And even looking to the sides:
http://i.cubeupload.com/s47l8r.gif
http://i.cubeupload.com/HXFRaC.gif

But, the motor control board had "something" wrong with it based
on what the plastic looked like:
http://i.cubeupload.com/0hFNfc.gif

I don't know what actually burned yet:
http://i.cubeupload.com/NzBAH1.gif

As the two capacitors seem to be intact:
http://i.cubeupload.com/DLgrxP.gif

Here's one of the capacitors at a side view:
http://i.cubeupload.com/LHKttV.gif

And here's the other capacitor:
http://i.cubeupload.com/eySoyP.gif

This shows a burned trace on the MMU:
http://i.cubeupload.com/zTTwBd.gif

And this shows a closeup of that:
http://i.cubeupload.com/pg2KkN.gif

As does this show burnt components or traces:
http://i.cubeupload.com/hXFq4P.gif

I don't think I can figure out, on my own, whether
it's repairable (I suspect it's not - do you?).

So, at this point, if you have good pointers for where to buy a
new Whirlpool motor control board (PN 8540540), I'd appreciate
more advice now that it's pretty sure that it's the MCU and not
the CCU.