According to this commentary published by Ronald Sokol the French court determined that an uncensored on-line discussion of teachers was too controversial. The court held that freedom of speech ended when it affected teaching. Huh?!
Teachers - and anybody other people for that matter - are already protected by laws against defamation or threats. The should not be above comment. And good ones shouldn't be afraid of being graded by their students. Bad teachers should be afraid - but what's wrong with telling the truth.
I understand that malice could enter into these grades and any on-line anonymous process could be tainted - but it is what it is. Take it for that and leave it at that.
Sokal's take on the subject is concisely given, "