Re: Bitcoin 20MB Fork

You are looking at it wrong. Transactions are signed with privatekeys. Same adresses have same privatekeys on both networks. Mpcoin nodes don't have to communicate with Gavincoin nodes to doublicate the transactions.

There are not two networks. There are two sets of nodes which disagree on which is the "One True Blockchain". Up until the fork (a certain block height) all the nodes have 100% agreement, but then after the fork, a subset, "MPnodes", start to reference utxo from blocks which are unknown to the Bitcoin nodes.
These tx are rejected by Bitcoin nodes just the same way, as if I created a tx for 123,000 BTC to send to an address I own, so I can have a nice fat bitcoin holding to rival the Winklevoss'.

Companies which accept bitcoins for products and services will be anxious to ensure that their nodes conform to the majority view and have the same blockchain that the exchanges, and payment processors do.

You don't get it. Nodes of the different networks don't have to communicate. Hashes are the same on both networks so anyone who watches the transactions on one chain can broadcast them on the other chain.

The majority of the people will make the step, there won't be a mess. I know me, and all of the miners I spoke to will make the step as well, as well as 90++% of all leading mining pools. Leaving you with a chain stuck with really high difficulty without enough hash to properly move it forward. When you finally do get it to the point where it readjusts difficulty you'll probably realize that it was incredibly stupid and that 1MBcapcoin is useless..... Maybe there will be people that will start using 1MBcapcoin to broadcast all their holdings to loads of different addresses, it won't matter because 1MBcapcoin won't be worth anything anyway.

i think 95% of people will stick with bitcoin core/satoshicoin/gavincoin and remove the 1MB transaction limit,
the other 5% chain will die out if difficulty is insanely high and there is not enough mining
power to match it

two chains will not co exist at 50% each ,theres just zero chance of that happening

Correct. Btc is btc.