I recently watched The Duellists and thought their uniforms were amazing; in particular their habit of wearing Pelisse coats like a cape; see an example here.
It seems amazing to me they wore their coats like this; how did this fashion develop and how popular was it? Were people that wore these kinds of coats considered a bit out there or was it just seen as completely acceptable?
I've written previously about the origins and evolution of Hussar uniforms here (with plenty of links to pictures). The habit of wearing a slung pelisse predated the Napoleonic wars by over a century.
Hussar units first appeared in Western European armies around the 1680's wearing costumes derived from Ottoman styles of the preceeding two centuries. These included capes made from animal pelts (for officers) or wool (for troopers) that were usually worn slung over the left shoulder so as to not interfere with the sword arm. Over the next few decades the cape merged the two materials becoming wool with a fur trim and by the 1720's had fully developed into the familiar pelisse - a short, fur-trimmed jacket with braiding to match the dolman.