Richard Adamfi wrote:
Posters have appeared at the entrances to Finsbury Park station
(famously without ticket gates) telling Pre-Pay Oyster users to touch
the validators entering and exiting the station.

That is fine - but this is followed by:

"Customers with Oyster Cards charged with Travelcard Season tickets
not valid at Finsbury Park (Zone 2) are also advised to touch their
cards on the validators"

Can someone explain what this is about?

They have these machines on the platforms at Highbury & Islington too.
Don't understand why anyone would swipe an Oyster or give up a Carnet
when they aren't forced to.

BTW hos do Oysters work on National Rail services?