I cannot see how a important change like this can be done without 95% consensus... I see people are saying that consensus can be reached at a
50%+ consensus for BU? { Please explain, because I am missing that point } ... I just love the fact that it is not easy to change important code in
the protocol, otherwise miners would have dominated these decisions... we still have a say.
We don't have a say. If 51% miners decide to change to a software with a different protocol the original chain will be changed. The 95% was just implemented in the segwit software. And BU has implemented 75% as far as I know...
No, this is not true. You only have no say with Segwit. If 51% of the miners implement segwit, all of them have to follow or get orphaned, and there will be only one chain. Whether your node supports segwit or not, only one single chain will be produced. No choice. Only miner majority. Core is nice to not activate before 95%, but they don't have to. 51% is enough.
However, with BU, you have a choice. BU being a HARD fork, (but backward compatible), it can make a NEW CHAIN forking off the normal bitcoin chain if it has 51% mining hash rate or more (if it has less, it will, being backward compatible, always be orphaned as it makes invalid blocks for the majority, but the standard chain is accepted by BU miners, which is the longest one).
So if BU goes beyond 51%, it makes a new chain WITH A NEW COIN, call it butcoin. Former bitcoin holders now hold their former stash of bitcoin, and a new, equal stash of butcoin. Bitcoin has forked. If exchanges include this butcoin, people can exchange butcoin for bitcoin and vice versa. The market cap of bitcoin will split over bitcoin and butcoin. If butcoin's market cap remains over 51% of the total, miners will stay in the majority with butcoin. We now have two coins: the original bitcoin, and an altcoin, butcoin.
However, if ever people sell off their butcoin for more bitcoin, and the market cap of butcoin drops, miners will move back to bitcoin (lower difficulty, higher market price). If now, butcoin becomes minority, a major clusterfuck happens.
Indeed, more miners on bitcoin means that sooner or later, the total PoW in the bitcoin chain will overtake the total PoW in the butcoin branch. From that moment on, butcoin miners will now accept the bitcoin chain as the valid chain, and mine on it (just to get orphaned each time by the majority: bitcoin's protocol being more severe, it is as if the former bitcoin protocol is a soft fork of butcoin so the majority wins). It is only if they implement a full hard fork that makes the bitcoin chain incompatible with the butcoin chain that the butcoin chain will not undergo this major orphaning.
But with a BU split, the market cap will decide, and as long as the market cap of butcoin is larger than bitcoin's, it will stay alive next to bitcoin. And if BU becomes fully incompatible with bitcoin, it will be an entirely different coin.