Ian's comment

draft-ietf-quic-transport.md

@@ -3806,10 +3806,11 @@ smaller maximum data than one found in an older packet.
 
 A sender SHOULD avoid retransmitting information from packets once they are
 acknowledged. This includes packets that are acknowledged after being declared
-lost. Doing so requires senders to retain information about packets after they
-are declared lost. A sender can discard this information after a period of time
-elapses, such as a PTO (Section 6.2 of {{QUIC-RECOVERY}}), or on other events,
-such as reaching a memory limit.
+lost, which can happen in the presence of network reordering. Doing so requires
+senders to retain information about packets after they are declared lost. A
+sender can discard this information after a period of time elapses that
+adequately allows for reordering, such as a PTO (Section 6.2 of
+{{QUIC-RECOVERY}}), or on other events, such as reaching a memory limit.
 
 Upon detecting losses, a sender MUST take appropriate congestion control action.
 The details of loss detection and congestion control are described in