user133124: Suppose a node begins broadcasting a signed transaction.
Question 1. At what stage is the signature verified? In §5 of the whitepaper, verification only appears during block acceptance after mining. Isn't it more sensible for a node to verify the signature on any transaction it tentatively places in a block?
Question 2. For how long does a node broadcast a transaction? How does it know when to stop broadcasting a transaction, either because it was accepted, or because it is invalid?

user5406: The whitepaper is only a high-level overview of Bitcoin, basically a marketing document. You may be interested in this errata and associated comments for the whitepaper created by David Harding.
Every node will verify the signatures on a transaction when it first receives it. If the transaction is deemed valid and passes is_standard policies, the node will then add the transaction to its mempool and relay it to the node's peers. The node will cache the result of the transaction verification for some time, to be able to skip repeating this check if the transaction is included in a block soon after.
A node will only rebroadcast a transaction once to all of its peers. However, the receivers and senders of transactions may rebroadcast transactions more often given their personal investment in the transaction's success if it doesn't confirm promptly.

133124: <p>Suppose a node begins broadcasting a signed transaction.</p>
<p><strong>Question 1.</strong> At what stage is the signature verified? In §5 of the whitepaper, verification only appears during block acceptance <em>after mining</em>. Isn't it more sensible for a node to verify the signature on any transaction it tentatively places in a block?</p>
<p><strong>Question 2.</strong> For how long does a node broadcast a transaction? How does it know when to stop broadcasting a transaction, either because it was accepted, or because it is invalid?</p>
 5406: <p>The whitepaper is only a high-level overview of Bitcoin, basically a marketing document. You may be interested in this <a href="https://gist.github.com/harding/dabea3d83c695e6b937bf090eddf2bb3" rel="nofollow noreferrer">errata</a> and associated comments for the whitepaper created by David Harding.</p>
<p>Every node will verify the signatures on a transaction when it first receives it. If the transaction is deemed valid and passes <code>is_standard</code> policies, the node will then add the transaction to its mempool and relay it to the node's peers. The node will cache the result of the transaction verification for some time, to be able to skip repeating this check if the transaction is included in a block soon after.</p>
<p>A node will only rebroadcast a transaction once to all of its peers. However, the receivers and senders of transactions may rebroadcast transactions more often given their personal investment in the transaction's success if it doesn't confirm promptly.</p>
