Add better explanatory comment

See https://github.com/matrix-org/synapse/pull/11114#discussion_r741304767

1 files changed, 3 insertions, 1 deletions

diff --git a/synapse/handlers/federation_event.py b/synapse/handlers/federation_event.py

index 9ccf99f5c5..f7573c1180 100644
--- a/synapse/handlers/federation_event.py
+++ b/synapse/handlers/federation_event.py
@@ -1474,7 +1474,9 @@ class FederationEventHandler:
         await self.persist_events_and_notify(
             room_id,
             tuple(events_to_persist),
-            # Events we fetch during backfill should be marked as backfilled as well
+            # Mark these events backfilled as they're historic events that will
+            # eventually be backfilled. For example, missing events we fetch
+            # during backfill should be marked as backfilled as well.
             backfilled=True,
         )