You are seriously confused about this aspect. There is no "majority hash rate consensus" between INCOMPATIBLE CHAINS. The only thing you do with your 51% hash rate is to produce INVALID BLOCKS wrt the original protocol. So this PoW doesn't matter, the blocks are invalid. If you produce 1.5 MB blocks with a PoW that is more than 10 times all the PoW that ever went into bitcoin, then these blocks doesn't count because they are simply INVALID. The old protocol simply rejects them (in the same way as if they were containing wrong signatures in the transactions). The only valid blocks (wrt the old protocol) are those, mined with the 49% hash rate of the miners sticking to the old protocol.
But the new protocol can continue building on its own chain with bigger blocks.
Of course, as long as BU accepts also old-protocol blocks, they need 51% of the hash rate, or the old chain (which is VALID under the new BU protocol if they don't protect themselves) will take over. In fact, in this case, you can see the old protocol as a soft fork from the BU protocol, which can IMPOSE its will when it is majority. In order to avoid that, BU should make the old protocol invalid too, so that ONLY BU blocks are compatible with BU. Maybe they could flip a little-endian/big-endian convention somewhere, so that both are fully incompatible. Otherwise, they risk at any moment to be killed by the "soft fork" of the old protocol.
Non BU blocks are still 100% compatible with BU so if BU doesn't have more than 50% of hash power, the fork will fail untless BU miners intentionally filter the non BU nodes. The only way for a fork to be successful is if the BU miners mine a block > 1 MB and have 51%+ of the hash power. Personally I'll wait until 18 blocks longer before I really consider the fork successful.
Yes, you are right (see the edit of my previous post). This "backward compatibility" of BU with respect to the standard protocol makes that the standard protocol is a soft fork of BU. Then they expose themselves AT ANY MOMENT to be orphaned, even 6 months later, if ever the BU fork falls beneat 51% hash rate. Then you will get the bitcoin chain orphaned 6 months behind, because from the first >1MB onwards, the soft fork is not compatible any more, and this will be the last valid block on the chain. Major clusterfuck !
The only safe way of making the BU hard fork, is by making it incompatible with the old protocol. If they don't do this, and they "pull the trigger", this will be a major disaster on the chain.
YOUR FORGETTING NODES aswell as POOL
learn real consensus
also your forgetting without banning communications. the minority see the blockheight. but then orphan it because the rules dont match.
then see the blockheight.. but then orphan it because the rules dont match.
then see the blockheight.. but then orphan it because the rules dont match.
then see the blockheight.. but then orphan it because the rules dont match.
endlessly.
BU wont ban the other community nodes.. only blockstream would ban the community nodes.
and that would only happen if blockstream were minority. because the community wont trigger unless they had majority.
and thats what blockstream fears.. losing their control where by the dozen other independant node brands continue.
remember and learn consensus
The only safe way of making the BU hard consensus, is by high majority If they don't do this, and they "pull the trigger", this will be a major disaster on the chain. with orphans. which eventually settles down to a single chain
leading to the minority either:
not syncing and just orphaning everything (dead in the water)
having to change their own protocol to match(re-joining the consensus community)
intentionally banning away from the majority to not see the higher blockheight and orphans to then build ontop of their MINORITY
FTFY