I showed my last post to a few people, and got some feedback on the idea. Robin pointed out that in this instance the chip and pin acts more like an anonymous provider rather than a transient provider, since the mechanism is not actually providing the identity, it is simply enabling the delivery of identity assertions. He says:

For the merchant, sufficient ‘proof’ of the cardholder’s ID is that they appear to have correctly entered the PIN. (Actually, of course, the merchant doesn’t give a toss if you’re the real cardholder, provided he is sure of getting paid. This accounts for why people have successfully signed for stuff as ‘Mickey Mouse’ &c).

Which makes a lot of sense. More to come on this in the next few days…