P2P guide - alerts

- Added alert details back

_includes/devdoc/guide_p2p_network.md

@@ -625,9 +625,21 @@ information. If a peer gets a banscore above the `-banscore=<n>` threshold
 
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-*Removed in Bitcoin Core 0.13.0*
+*Removed in Bitcoin Core 0.13.0. Retained in Dash Core (see [PR1326](https://github.com/dashpay/dash/pull/1326)).*
 
-Earlier versions of Bitcoin Core allowed developers and trusted community members to issue [Bitcoin alerts](https://bitcoin.org/en/alerts) to notify users of critical network-wide issues. This messaging system [was retired](https://bitcoin.org/en/alert/2016-11-01-alert-retirement) in Bitcoin Core v0.13.0; however, internal alerts, partition detection warnings and the `-alertnotify` option features remain.
+In case of a bug or attack, the Dash Core developers can issue an alert via the
+Dash network. Alerts will be displayed by the Dash Core UI. Users can also
+check the error field of the `getinfo` RPC results to get currently active
+alerts for their specific version of Dash Core or use the `-alertnotify` command
+line parameter to specify a custom command to execute when an alert is received.
+
+These messages are aggressively broadcast using the `alert` message, being sent
+to each peer upon connect for the duration of the alert. These messages are
+signed by a specific ECDSA private key that only a small number of developers
+control.
+
+**Resource:** More details about the structure of `alert` messages and a
+complete list of message types can be found in the [P2P reference section][section P2P reference].
 
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