On this model Hohner, the reed plate is removable (screwed in place). I removed the reed plate and put it in the dishwasher as well. So four parts were in the dishwasher as separate entities: top cover, bottom cover, reed plate, and main chassis with key assemblies.
I repositioned all four parts about every ten minutes including the reed plate to ensure even exposure to the water jets. I was careful in handling the reed plate so that it would not fall over and maybe push a reed tip into one of the dishwasher tines. I used whatever dishwasher soap was under the counter. Cascade packets I think. The water gets pretty warm, but not warm enough to affect the reed plate. The reed plate remained in perfect tune.
All the parts came out looking really bright and clean.
I took the parts out after an hour because the paint on the burgundy covers appeared to be getting hazy. As soon as I took the covers out and wiped them down, they were fine. I think exposing the adhesives/sealers/felts to more than a hour of warm soapy water is probably pushing the limit.
The experiment is not over quite yet. I don’t have experience with the long term effect. Maybe the valve pads will all disintegrate in four weeks. I don’t know. But I am pretty confident all will be well for some time.