Bikes on the DLR

It does not have to be adequate for Canary Wharf alone - it is a suplement to the jubilee line surely?

Not sure what you mean--it was obviously built long before the Jubilee Line Extension.

Of course, there are other means of accessing CW by public transport, but the DLR is still the only railway line along the alignment from the City to CW (and most of its other branches, including the only railway line to cross under the river at Greenwich).

Stratford is served by numerous overground routes, Jubilee line and DLR - I'd guess that the DLR accounts for under 5% of users of the station.

Again, the DLR serves particular alignments where there is no other rail line. All users wishing to go where the DLR goes suffer from its imperfections.

The DLR fulfills a completely different role to the tube... the stations tend to be closer and it should be regarded as a super-tram as much as it should be regarded as an inferior tube.
Many cities permit cycle carriage on trams (see towards the end of this presentation):

http://www.cyclenation.org.uk/papers/031003.pdf

The closeness of the stations isn't a major factor. Passenger volume and the safety constraints cited in the DLR e-mails are much more important.

The simple fact is that the DLR was never designed as a railway line that permitted cycle carriage, although it could have been. It was designed more like a glorified airport shuttle.