French user of YARPP here. I've been using it for a long time now, and I just noticed that the keyword selection wasn't effective at all for french language. So I managed to make it better.
Here's a list of "overused" words (ready to use in YARPP after a small modification in intl.php) : http://goo.gl/LF7J2 . This list was compiled after a list of french words ordered by frequency of use ( http://eduscol.education.fr/cid47916/liste-des-mots-classee-par-frequence-decroissante.html )
I also noticed that when using wp-Typography, YARPP is completely messed up with keyboard, eg. using half-words as keywords... Probably because of the hyphenation feature. Would be great to fix that!
Hope you will take my contribution in consideration and thanks for this great plugin!