Add docs

src/main/java/refinedstorage/gui/GuiGrid.java

@@ -5,6 +5,7 @@ import net.minecraft.client.gui.GuiScreen;
 import net.minecraft.client.gui.GuiTextField;
 import net.minecraft.client.renderer.GlStateManager;
 import net.minecraft.client.renderer.RenderHelper;
+import net.minecraft.entity.player.EntityPlayer;
 import net.minecraft.init.SoundEvents;
 import net.minecraft.item.Item;
 import net.minecraft.item.ItemStack;
@@ -295,6 +296,11 @@ public class GuiGrid extends GuiBase {
         }
 
         if (isOverSlotWithItem()) {
+            /**
+             * Some mods modify the NBT tag in {@link Item#addInformation(ItemStack, EntityPlayer, List, boolean)}
+             * and that would cause a client and server desync between the items and
+             * that makes pulling fail.
+             */
             drawTooltip(mouseX, mouseY, items.get(slotNumber).copy());
         }