ch-07: add caveat re 3rd party malleability and segwit

07_payment_channels.asciidoc

@@ -329,7 +329,7 @@ Alice has to depend on the transaction ID of the funding transaction being known
 
 If Bob could modify Alice's funding transaction before it was confirmed and produce a replica that had a different transaction ID, Bob could make Alice's refund transaction invalid and hijack her bitcoin. Alice would be at Bob's mercy to get a signature to release her funds and could easily be blackmailed. Bob couldn't steal the funds, but he could prevent Alice from getting them back.
 
-The introduction of SegWit made unconfirmed transaction IDs immutable, meaning that Alice could be sure that the transaction ID of the funding transaction would not change. As a result, Alice can be confident that if she gets Bob's signature on the refund transaction, she has a way to recover her money. She now has a way to implement the Bitcoin equivalent of a "prenup" before locking her funds into the multisig.
+The introduction of SegWit made unconfirmed transaction IDs immutable from the PoV of 3rd parties, meaning that Alice could be sure that the transaction ID of the funding transaction would not change. As a result, Alice can be confident that if she gets Bob's signature on the refund transaction, she has a way to recover her money. She now has a way to implement the Bitcoin equivalent of a "prenup" before locking her funds into the multisig.
 
 [TIP]
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