diff --git a/lib/setuplib.php b/lib/setuplib.php
index 2cdd8f22e1a..7a352781366 100644
--- a/lib/setuplib.php
+++ b/lib/setuplib.php
@@ -910,9 +910,16 @@ function initialise_fullme() {
         $_SERVER['SERVER_PORT'] = 443; // Assume default ssl port for the proxy.
     }
 
-    // Hopefully this will stop all those "clever" admins trying to set up moodle
-    // with two different addresses in intranet and Internet.
-    // Port forwarding is still allowed!
+    // Using Moodle in "reverse proxy" mode, it's expected that the HTTP Host Moodle receives is different
+    // from the wwwroot configured host. Those URLs beeing identical could be the consequence of various
+    // issues, including:
+    // - Intentionally trying to setup moodle with 2 distinct addresses for intranet and Internet: this
+    //   configuration is unsupported and will leads to bigger problems down the road (the proper solution
+    //   for this is adjusting the network routes, and avoid relying on the application for network concerns).
+    // - Misconfiguration of the reverse proxy that would be forwarding the Host header: while it is
+    //   standard in many cases that the reverse proxy would do that, in our case, the reverse proxy
+    //   must leave the Host header pointing to the internal name of the server.
+    // Port forwarding is allowed, though.
     if (!empty($CFG->reverseproxy) && $rurl['host'] === $wwwroot['host'] && (empty($wwwroot['port']) || $rurl['port'] === $wwwroot['port'])) {
         throw new \moodle_exception('reverseproxyabused', 'error');
     }