I did not polish the faces of the LEDs, I left them rough-ground.

This is an interesting thread!

I'm guessing that when you grind the LED, you add facets to the glass that bounce light in different directions. Re-polishing it would seem to defeat the purpose.

I also like genixia's silicon putty idea. maybe a combination of both? Unmodified, if the LED's light is focused and transmits through an air gap, it wouldn't tend to disperse, but if you can get it to disperse through ersatz facets in the LED, then disperse even further through a silicone gap (instead of air) then that seems promising. Personally, I don't care if the buttons wind up very bright. Subdued would work for me.

Yeah, reversing the LEDs would be a stretch -- might do something on the buttons because of the white plastic surrounds, but not of any use on the SM knob LEDs ('course less of an issue there, I think...).

I took a look at the button LEDs under a microscope and it looks like you could shave at least 1/3 of the glass without endangering the LED internals. I may have to follow genixia's advice and get a bunch of small white LEDs from Radio Shack and experiment.