Re: Forked block chain

I don't understand your objection. The coins that are valid on both sides of the fork have nothing to do with each other.

The point is that if you sign the transaction in one fork, the recipient can submit the same transaction to the main chain and also get your coin there.

But how is re-broadcasting prevented in the main chain as it is?

Re-broadcasting from where? You need the private key to sign the transaction.