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).