The footnote got me curious about Segwit2x replay protection, so I went to find how it works[1]. Essentially, strong replay protection would work automatically

The footnote got me curious about Segwit2x replay protection, so I went to find how it works[1]. Essentially, strong replay protection would work automatically but force wallets and other software to upgrade to use the forked chain. Opt-in replay protection allows existing wallets to be used with the fork immediately. Whether this is good or bad really depends on who you ask, I suppose. From Bitcoin.org's perspective, they see this lack of strong protection as a way for the Segwit2x chain to steal coins from the 'real' chain. From the Segwit2x perspective, they see this as maintaining compatibility under the assumption that they will become the main (essentially only) chain. Opt-in protection seems like a negative if the chains continue to coexist for a long time, since both chains will be vulnerable. It only makes sense if you think it one chain will die off. And yet, I could see Opt-In replay protection encouraging the chains to merge, as users are slightly incentivized to pick a chain rather than deal with replay protection indefinitely. The beauty of the blockchain is that we will see this all play out publicly, and learn from the results [citation needed]. [1] https://bitcointechtalk.com/how-segwit2x-replay-protection-works-1a5e41767103 https://bitcointechtalk.com/how-segwit2x-replay-protection-w...