Re: bitsofproof supernode vulnerability: block chain split / node isolation

I don't think so. Check https://en.bitcoin.it/w/images/en/7/70/Bitcoin_OpCheckSig_InDetail.png

The script scriptSig is completely removed from the transaction when the hash is performed. It's replaced by a part of the previous scriptPubKey.

Yes, but the value part of the TxOut structure would be different isn't it ? That is part of the hash.