This one made me think of you, Hoody:
It was prompted by the news of the upcoming christening of Prince Louis of England.
"Louis" has a silent 'e'. Lou-ee.
But since "Louis" ends in 's', we don't put a new 's' after the apostrophe.
So now we have "Prince Louis' christening" and how to do we pronounce it?
The 's' before the apostrophe is still silent, but now we pronounce a nonexistent 's' after the apostrophe.