Re: [Bitcoin-development] First-Seen-Safe Replace-by-Fee

[Gregory Maxwell <gmaxwell@gmail.com>]

On Tue, May 26, 2015 at 5:54 PM, Tom Harding <tomh@thinlink.com> wrote:
>  It's not difficult to
> imagine real-world consequences to not having contributed to the
> transaction.

I'm having a hard time. Can you help me understand a specific case
where this makes a difference.

It appears to be a gratuitous requirement;  if I have another unused
input that happens to be larger by the required fee-- why not just use
it?

The inherent malleability of signatures makes it unreliable to depend
on the signature content of a transaction until its good and buried,
regardless. And an inability to replace an input means you could not
RBF for additional fees without taking change in more cases; there
ought to be a benefit to that.