On Tue, Sep 5, 2017 at 10:51 PM, Jorge Timón via bitcoin-dev <
bitcoin-dev@lists.linuxfoundation.org> wrote:

> Is there any reason or use case to keep allowing spendable outputs
> with null amounts in them?
>

Someone could have created a timelocked transaction that depends on a zero
value output.

This could be protected by requiring a tx version number change.  Only zero
outputs in the new version would be affected.

I am not sure how strictly people are sticking to that rule though.