Quote from: Peter Todd
So your security assumption goes from not being sybilled, and no miner collusion, goes to "and I am not censored from other nodes which altogether do 100% validation" (for receiving fraud proofs). This is a far-more scalable full-node or partial-full-node model that we could evolve to. It's a security tradeoff. It's certainly not one that everyone would want to make, but it doesn't effect those who wouldn't want that.
It was not said by Peter Todd, but Pieter Wuille in his original Segwit presentation:
http://diyhpl.us/wiki/transcripts/scalingbitcoin/hong-kong/segregated-witness-and-its-impact-on-scalability/ he was talking about the possibility of a new kind of node between SPV and full node, and it has nothing to do with the full node security during a hard fork. Cypherdoc misrepresented it as " and since one of the stated benefits of SWSF was that it shifts the security assumptions away from miner collusion and non-Sybiling to that of "non censored partially validating SPV node connections" via as yet uninvented/coded fraud proofs in an attempt to scale nodes, this just compounds the problem given that we now know that the p2p network in a SWSF can be parititioned. we can't tell if SWSF is safe."
Your full node would not be downgraded to a "fraud-proof" node in the scenario of a SWSF, AFAIK the code for fraud proof has not even been written(he did mention that, but apparently contradicting himself), it's until now a mere theoretical construction.