But Satoshi posted the first text message in the blockchain (bank bailout)...
If you ask me, that was a mistake, but many people (especially BSV/big blockers) will disagree, because they don't see it as a mere payment system.
No, it was not a mistake to quote the newspaper as this was needed to prove that the Genesis block and further blocks weren't pre-mined.
It was also to my knowledge the only time that Satoshi Nakamoto included such data into blocks he mined. He clearly didn't see the blockchain as something to store superfluous bullshit or bloat it with stuff that doesn't have much to do with Bitcoin transactions details.