I've used lots of non-breaking thin spaces in Les misérables
. It works fine in my reader, does it work in others? It should be relatively easy to convert them to something else.
P.S. I've seen much French printed
stuff with what I believe is plain incorrect typography: uneven spacing inside quotes (« like this»), line breaks just before a question mark (clearly someone typed a normal space in the word processor), etc. It's always in some "second class" material, though: TV magazines, comic books (not that the comic book is second class, but the printed text parts didn't obviously receive much attention).