“Isn’t that apostrophe “Mes Amis” just a slightly misplaced acute accent from the “e”?“
If it is then that’s entirely incorrect, too 🙂
“I was taught at school (especially for RS exams) that the correct possessive was Jesus’ or Charles’ (hiatory exams) etc. But these days, Jesus’s, Charles’s or Chris’s seem equally common or even preferred.“
I’m not sure I can remember exactly what I taught, but I write as I would naturally say it. Which means I use “with s” for singular possessors (“Jesus” and “Chris” seem prime examples of why, as they end with a soft “s”. You wouldn’t say “Ooh, I like Jesus hair today;” you’d say “Ooh, I like Jesus’s hair today”) and just the apostrophe for most plurals (if talking about the timesheets of a number of nurses, it would be odd to say “the nurses’s timesheets”). As always with language, there are exceptions 🙂