Update EP comment

Marlin/Configuration_adv.h

@@ -1792,10 +1792,14 @@
   //#define SERIAL_STATS_DROPPED_RX
 #endif
 
-// Enable an emergency-command parser to intercept certain commands as they
+/**
-// enter the serial receive buffer, so they cannot be blocked.
+ * Emergency Command Parser
-// Currently handles M108, M112, M410
+ *
-// Does not work on boards using AT90USB (USBCON), ESP32, STM32F1/4/7, or Teensy 3.5/3.6 processors!
+ * Add a low-level parser to intercept certain commands as they
+ * enter the serial receive buffer, so they cannot be blocked.
+ * Currently handles M108, M112, M410, M876
+ * NOTE: Not yet implemented for all platforms.
+ */
 //#define EMERGENCY_PARSER
 
 // Bad Serial-connections can miss a received command by sending an 'ok'