PSA: New trick to ban yourself. Please read.

Every interaction between the client and server is through packets.
Almost every single action in the game is controlled through packets sent by the client and packets sent by the server.

While many actions in the game do have a call and response from the server, it is believed that opening your inventory and equips is not one of them.

You can open your Inventory, Equips, and Walk around while the server lags and does not respond. You cannot however, talk to an NPC.