We learn a number of very interesting things in this chapter. I'll focus on one area

-Like with horcrux sspell, abssurdity [of the stone] hidess true ssecret. -True Sstone iss not what that legend ssayss. -True power iss not what sstoriess claim. -Sstone iss powerful healing device in truth.

So it's confirmed it exists and that it isn't what people think and that it's power / mechanism isn't what people think.

This is important because thinking back to Harry's early experiments with Hermione, he discovered that if you don't know what a spell does or have been told something completely in the wrong space the spell doesn't work at all. If you know generally what it does, it still works as long as you pronounce it correctly. (The later is also confirmed by the 'for enemies' spell).

In the library Hermione told Harry that the spell is published but no one has been able to actually perform it (nominally due to difficulty). If they all think it does something other than what it actually does, that explains it and is consistent with the book's theory of magic.

Also worth noting, Hermione was killed shortly after she began looking into the stone in earnest.

-Sstone's ssuppossed maker wass not one who made it. -One who holdss it now, wass not born to name now ussed. -One who holdss Sstone iss repossitory of much lore. -Taught sschoolmasster many ssecretss.

This part also seems very important. We get a new "major player". This player is powerful enough that QQ couldn't just take the stone and also powerful enough to have taught Dumbeldore many things (and Dumbeldore is thought to be the most powerful wizard in centuries). So here is a behind the scenes power on par or stronger than either major player in the last war.

Nick Flamel seems to just be the most recent alias for this other player, who has probably been around for a long time. For my money, I predict NF is really Baba Yaga ("the undying"). She's been named dropped too often to not make an appearance, and her being NF allows her to have been around all along instead of being an unsatisfying last chapter walk on.