This was just posted to one of my Facebook groups, by a native English speaker who is reading the Harry Potter series in French. She commented on how the names are translated:

- Gryffindor > Gryffondor
- Ravenclaw > Serdaigle ("aigle" means "eagle")
- Slytherin > Serpentard
- Hufflepuff > Poufsouffle

- Draco > Drago
- Snape > Rogue (!! A completely different name for one of the most important characters! I guess "Snape" doesn't evoke much in French, since neither "Snake" nor "Snipe" are words. "Rogue" means the same in French as in English.)
- Prof. Sprout > Prof. Chourave ("kohlrabi"!! Hahaha)
- Hedwig > Hedwige
- Neville LongBottom > Neville Londubat (something like "far from the beat")
- Mrs Norris the cat > Miss Teigne (literally "nagger")
- Scabbers the rat > Croutard (direct translation of "Scabbers")
- Nearly-Headless Nick > Nick Quasi-Sans-Tete (literal)
- Moaning Myrtle > Mimi Geignarde ("Whining Mimi")
- Madam Hooch > Madame Bibine ("Madam Booze")
- Tom Marvolo Riddle > Tom Elvis Jedusor. They had to come up with a whole new anagram: "I am Lord Voldemort" > "Je Suis Voldemort". Also, "Jeu du Sort" means "game/riddle of fate". IMPRESSIVE.

- Muggles > Moldus
- Diagon Alley > Chemin de Travers ("Way/Path Through")
- Knockturn Alley > Allee des Embrumes (literally "Knockturn Alley"... without the pun)
- Mudblood > Sang de Bourbe (Mired Blood, or maybe BloodMire)

I wondered if they would change any of the names that are just straight-up French words, so it's not so... you know, obvious. But nope! French people are literally reading about a villain named "Flight of Death". lol. The surname of Harry's school enemy is "Done Badly" or possibly "Bad Time". lolol. And no-one can guess that the werewolf might be the new professor whose name is "Professor Wolf".