A bakers couch is just floured fabric, whats the advantage to using it? King Arthur's site says that it promotes chewy, crunchy crust - how's that? If I'm just keeping it floured and not washed all the time, isn't there a risk of some kind of bacteria, or should it just be too dry?
The bakers couche is not just floured fabric, it is usually a hard wearing canvas
It is used to allow the dough to breath, and hold it's shape while your actual bread moulds are being used in the oven. The all over air gap allow the crust to dry slightly. A dry crust makes it easier to handle and bakes slightly more crispy
The flour is there to stop the soft dough from sticking to the canvas, but a with careful handling and a well worn in couche this should not happen
If you keep the couche dry it should not develop mold or mildew. Even if it does, leave it out in the sunshine, so that the UV light can deal to it. I can't imagine that the occasional normal household mold is going to form dangerous toxins that can survive the oven!
After use, give the couche a good brush down with a clean fine bristled brush, and store somewhere dry
If you have plenty of the fine perforated steel moulds, you wont need to use a couche, just use the pans