Don't let chat/console eat inputs from anyone besides player 1

src/console.c

@@ -745,9 +745,35 @@ boolean CON_Responder(event_t *ev)
 	// check for console toggle key
 	if (ev->type != ev_console)
 	{
+		INT32 i, j;
+
 		if (modeattacking || metalrecording)
 			return false;
 
+		if (splitscreen && ev->data1 >= KEY_MOUSE1) // See also: HUD_Responder
+		{
+			for (i = 0; i < num_gamecontrols; i++)
+			{
+				for (j = 0; j < 2; j++)
+				{
+					if (gamecontrolbis[i][j] == ev->data1)
+						return false;
+
+					if (splitscreen > 1)
+					{
+						if (gamecontrol3[i][j] == ev->data1)
+							return false;
+
+						if (splitscreen > 2)
+						{
+							if (gamecontrol4[i][j] == ev->data1)
+								return false;
+						}
+					}
+				}
+			}
+		}
+
 		if (key == gamecontrol[gc_console][0] || key == gamecontrol[gc_console][1])
 		{
 			if (consdown) // ignore repeat

src/hu_stuff.c

@@ -1056,12 +1056,44 @@ static boolean justscrolledup;
 boolean HU_Responder(event_t *ev)
 {
 	INT32 c=0;
+	INT32 i, j;
 	
 	if (ev->type != ev_keydown)
 		return false;
 
 	// only KeyDown events now...
-	
+
+	// Shoot, to prevent P1 chatting from ruining the game for everyone else, it's either:
+	// A. completely disallow opening chat entirely in online splitscreen
+	// or B. iterate through all controls to make sure it's not bound to another player's
+	// You can see which one I chose.
+	// (Unless if you're sharing a keyboard, since you probably establish when you start chatting that you have dibs on it...)
+	// (Ahhh, the good ol days when I was a kid who couldn't afford an extra USB controller...)
+
+	if (chat_on && splitscreen && ev->data1 >= KEY_MOUSE1)
+	{
+		for (i = 0; i < num_gamecontrols; i++)
+		{
+			for (j = 0; j < 2; j++)
+			{
+				if (gamecontrolbis[i][j] == ev->data1)
+					return false;
+
+				if (splitscreen > 1)
+				{
+					if (gamecontrol3[i][j] == ev->data1)
+						return false;
+
+					if (splitscreen > 2)
+					{
+						if (gamecontrol4[i][j] == ev->data1)
+							return false;
+					}
+				}
+			}
+		}
+	}
+
 	if (!chat_on)
 	{
 		// enter chat mode