[myself248]

Oooo, #1 is fascinating. I've always used liquid and never considered this. I always run with the extra rinse enabled and no softener, so the fabrics come out clean enough that they don't smear optics. I really don't think anything's left behind, but it's an interesting theory.

7: I'm 99% sure none of my washers have ever had an integrated lint trap. I ziptie a mesh-sock trap onto the drain hose so it doesn't clog the washtub drain, and the amount of stuff it accumulates means that any machine-internal lint trap would've been clogged solid in the first few months. There's no mention of one in the manual, either.

I wonder if I didn't drain it upward into a washtub, but downward into a floor drain, if that would eliminate the water-left-in-hoses problem...

[sumtechguy]

It is not much of a 'trap' it is basically a plastic filter just before the drain out. Think it mostly is to keep big stuff out of the sump. But bits of cloth and hair can get stuck on it. You also probably do not want to totally drain it all the time. The sump as someone else pointed out needs to stay wet.

On mine it is a circular item that you can twist out. If I do it before draining water comes dumping out of that. So I drain then clean that thing. Bit of hot water and a bit of scrubbing.