I read that article in the link you posted, Daox. Good article. It sounds like it's possible to air seal a dryer after a fashion but not perfectly and since it's not insulated the dryer still radiates heat. He also found that the dryer blower wasn't sufficient alone with a 6 inch duct from the attic. That was good to know.
I think I'll try to stick with the idea of isolating the room, rather than the dryer. I had been planning on pumping in cellulose in the walls of the laundry room just to quiet it down. Now there's another reason to do it. It looks like I'll be modifying my system (yet again
) with a 12" branch duct from the main duct from the attic to the laundry room ceiling. I'll have to do some thinking whether I can get away with a makeup air damper in that line or whether I will have to use an actively controlled damper to stop interaction with the makeup air dampers for the whole house fans?? I might be able to get away with a makeup air damper if I can get a tight fit on the door to the laundry room.