I've got some queries that might take a bit of working out and could
take a bit of time and money to test.

The PAYG fare from the southern end of the DLR to Bethnal Green (zone
2) is £1, which presumably means that it is assumed to involve going
via Stratford.

If one went on PAYG via Bank, touching only at the start and end of
the journey, it wouldn't know the difference and would charge £1, and
anyone checking on the way would see that you'd touched in and have no
complaint.

Question 1: If you touched at the mysterious readers at Bank DLR,
would it treat it as a continuation of a journey nevertheless always
priced at £1, or would it work out that you'd been via zone 1 and
charge £1.50/£2?

If you had a zone 1 and 2 travelcard loaded on the Oyster, went via
Bank and didn't touch beforehand, it would let you through the gates
at Bethnal Green and would be valid if it was checked on the DLR on
the way to Bank whether you touched in or not.

Question 2: If you touched the travelcard on entering the DLR, would
it just acknowledge that it was valid, or would it figure that you've
used a zone 1 and 2 travelcard on a journey priced as involving zone
3, and deduct the extension fare, in which case would it be one
extension or two?

(I think probably not, but if so I'd have hit on a way that you would
pay extra by touching a travelcard valid for the whole of the DLR
journey, nevertheless unfairly.)

Question 3: In the unlikely event of the answer to question 2 being
that you'd be charged an extension for zone 3, could this be avoided
by touching the mysterious readers at Bank?