-snip-So if it's possible to extract the private key from the signature, every unspent transaction in the blockchain should've been stolen by now.
This is a little misleading as
those stolen transactions could be stolen again by other people, and then again and again, making the Bitcoin network worthless in the process. It's not a "central party steals all the bitcoins for themselves" kind of thing.
".
Thanks for the mention.
That post is simply explaining why Bitcoin wont work if his query is possible.