Add a comment about non-functional bot code

code/game/ai_dmq3.c

@@ -2876,6 +2876,7 @@ float BotEntityVisible(int viewer, vec3_t eye, vec3_t viewangles, float fov, int
 		BotAI_Trace(&trace, start, NULL, NULL, end, passent, contents_mask);
 		//if water was hit
 		waterfactor = 1.0;
+		//note: trace.contents is always 0, see BotAI_Trace
 		if (trace.contents & (CONTENTS_LAVA|CONTENTS_SLIME|CONTENTS_WATER)) {
 			//if the water surface is translucent
 			if (1) {