This debate is not by any means specific to this site.
I googled -'hardened valve seats unleaded'- and there is no real consensus, Chevron claims all passenger cars and light trucks are safe from valve recession.
They even say that antique cars actually benefit from unleaded because of less exhaust corosion and oil contamination.
But we can't expect them to say "hey our fuel will ruin your ride".
And of course there are tons of articles that say exactly the opposite, I think it is safe to say that if you plan to operate under heavy loads or at high RPM's then hardened seats are a pretty good idea.
