Move note on return values to the interface documentation

DBusInterface.md

@@ -18,6 +18,11 @@ object. Properties marked as 'mutable' may change, and a
 `org.freedesktop.DBus.Properties.PropertyChanged` signal is sent for those
 unless otherwise specified.
 
+All setters (whether implicit for read-write properties or explicit) return
+success instead of the internal return value because DBus does not like
+non-standard error values. This means that clients should check for capabilities
+beforehand and that the `Commit()` method (see below) signals an error.
+
 org.freedesktop.ratbag1.Manager
 ===============================
 

ratbagd/ratbagd-profile.c

@@ -373,12 +373,6 @@ ratbagd_profile_set_name(sd_bus *bus,
 					       NULL);
 	}
 
-	/*
-	 * Note: we should return `r`, but the d-bus bindings doesn't
-	 * like non standard errors. So just return success and let the client
-	 * check for the capability before-hand and let .commit() signal an
-	 * error.
-	 */
 	return 0;
 }