diff --git a/.env.example b/.env.example
index 18fa8d4..eea2f47 100644
--- a/.env.example
+++ b/.env.example
@@ -24,6 +24,8 @@ MQTT_PASSWORD=
 MQTT_TOPIC_FILTER=/+/+
 # 0 = at most once, 1 = at least once (duplicate rows possible after reconnects)
 MQTT_QOS=1
+# Unique per deployment! Two clients with the same id on one broker kick each
+# other off in a reconnect loop (e.g. local dev instance vs production stack).
 MQTT_CLIENT_ID=nodeledge-mqtt-listener
 
 # Keys the listener injects into every payload.