On Wed, Sep 16, 2015 at 9:19 PM, Rusty Russell <rusty@rustcorp.com.au> wrote:

I couldn't see a use for it, since partial enforcement of a soft fork is
pretty useless.

It isn't useful for actually using the feature, but some miners might set the bit but not actually create blocks that comply with the new rule.

This would cause their blocks to be orphaned until they fixed it.

OK, *that* variant makes perfect sense, and is no more complex, AFAICT.

So, there's two weeks to detect bad implementations, then you everyone
stops setting the bit, for later reuse by another BIP.

It could be more than two weeks if the support stays between 80% and 90% for a while.

75%+ checks that blocks with the bit set follow the rule.

95%+ enters lock-in and has the same rules as 75%+, but is irreversible at that point.

You need a timeout: an ancient (non-mining, thus undetectable) node
should never fork itself off the network because someone reused a failed
BIP bit.

I meant if the 2nd bit was part of the BIP. One of the 2 bits is "FOR" and the other is "AGAINST". If against hits 25%, then it is deemed a failure.

The 2nd bit wouldn't be used normally. This means that proposals can be killed quickly if they are obviously going to fail.