1. I thought we already decided that excluding transactions was not a possible attack (unless 100% of peers are evil), because the honest fork would be readily identified as including all transactions (including those from the evil fork). The worst that could happen is a transaction could be delayed by one CB period, if the evil fork withheld propagation of TBs (to non-evil peers) until the CB (where it can't be withheld any more and still be a public fork) or if the evil fork included transactions from the honest fork one CB later (so as to be not readily identified as the evil fork).
Things are as not as simple, because if we count the branch with more transaction as the honest one, then the attacker can introduce his own transaction which wasn't broadcasted, and win. So in practice you don't know whether it's a transaction which has been dropped or added by an attacker. The time limits resolve this.
Incorrect, because every fork can pick up this transaction in its next CB. The evil fork has to broadcast the CB else the fork doesn't exist in public view.
2. The only attack vector is that evil peers will not let non-evil peers sign their CBs and evil peers could create one or more forks in addition to the honest peers. There might even be multiple factions of evil peers who don't want to share tx revenue and thus exclude other peers. So the problem is how to identify which fork is the consensus in order to properly award tx fees?
The proposed resolution of this is by timing. If you introduce some precise time windows when a message must be broadcasted, then the nodes who are always online can decide whether the protocol was followed. The protocol can be modified such that if an SH decides to not include a TB in his CB, he must declare that immediately at the time of that TB. In this way CB is built continuously and not just decided last minute, so there can be no surprises at the time of CB. Therefore anyone who observes the process can decide if TBs are being withheld or being dropped dishonestly. Etlase2 had a more elaborate solution above.
This doesn't solve a non-problem that doesn't exist with transactions. It does nothing to solve the 51% attack with signing of the CB. Signing of the CB is necessary to decide the order of peers who can sign TBs.
b. The honest peer's opinion is only valid for himself, and can't be proven to the world without 51% consensus.
True. But the ability of the honest always-online node to see through 51% attack with just passive observation is already a good start.
No it accomplishes nothing as I already explained. We are walking in circles going no where. The 51% attack can not be avoided by any decentralized design.
I want to stop wasting time and move to things we can accomplish on fixing other Bitcoin weaknesses.