Guido wrote:
Now I'm pondering how best to protect the deck's wood surface from
movements of those metal deck chairs?

Rubber feet? Cork on the feet?

Is there a product which will glue on / wrap around chair legs that
works well?

http://www.bjburycats.com/floorprotectorskitty.html

Well, maybe not your style. (Maybe not anyone's style.)

http://www.growinglifestyle.com/article/s0/a919491.html

And if you're cheap ...

http://www.growinglifestyle.com/article/s0/a461376.html