On Sat, Dec 26, 2015 at 8:23 AM, Eric Lombrozo via bitcoin-dev <bitcoin-dev@lists.linuxfoundation.org> wrote:

Unfortunately, this also means longer confirmation times, lower throughput, and lower miner revenue. Note, however, that confirmations would (on average) represent more PoW, so fewer confirmations would be required to achieve the same level of security.

No, the re-target compensates so that the number of blocks in the last two weeks is 2016. If a soft fork forces miners to throw away 25% of their blocks, then the difficulty will drop by 75% to keep things balanced. Throwing away 75% of blocks has the same effect on difficulty as destroying 75% of mining hardware.

The block interval will only increase until the next re-target.

Slowly increasing the fraction of blocks which are thrown away gives the re-target algorithm time to adjust, so it is another advantage.

If the rule was instantly changed so that 95% of blocks were thrown away, then there could be up to 40 weeks until the next retarget and that would give 200 minute block times until the adjustment.