These characters are among some of the characters that display as emojis using the server's texture pack:
You can use these in chat any time! Just make sure to start your message with some English word in the beginning, or else the server will block your next message (this is a glitch, you can't send 2 Chinese messages in a row, even if they are different messages)
There is a glitchy map (map_7598) at the coordinates -407.50 104.50 -807.97 (Spirited Away map). It draws and updates that map when you fly around with it in your hand.
Another glitched map is at 3961.97 141.50 -3213.50 (at /warp Howls_Castle, map_9010). The minecraft:armor_stand at 3956.53 140.20 -3228.96 is wearing a player head with a missing texture.
There are possibly many other maps and armorstand playerheads in the world that are like this.