This is such a great discussion. I know the feeling of not wanting to wear a precious scarf, I even got backups for some (2 vert amande phoenix, both full price, the other very preloved with faults that I got for very cheap). But on the other side: If it is not soaring hot outside I wear a H scarf whenever I leave the house. I might be overdressen when shopping for groceries, but I do not care. Sometimes nobody will see them underneath a warm jacket, but I love how it feel around my neck. For my funeral wrap me in that faded Mare aux Canards that I wear all the time for cycling but sell it's good (almost unworn) twin for charity!
But when it comes to food: sling them to the back, hide under blouse, take off entirely. Sweat can be washed easily, red pesto not so much.
On the other side: wearing an H scarf daily kind of makes it harder to dress up: I do not look this much more polished when going out, dramatic drapes of 140cm-scarves are what I try to do.
I can relate the worries about the Mont Saint Michel plissee: It is very old, thus I would worry more about color runs. The plissee might get ruined (from washing as well as from knotting, my cosmos has lost some of it's folds), it is such a precious one and near impossible to get a backup. I might save this one for special occasions like going to the opera.