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I have complained about the wording of that error all the way back to the beta testing days.
Messaging in this context has nothing to do with chat but rather "messages" your game client is sending to the server.
For example, if you spam the block key a million times in 5 seconds, your client will send a "Hey, i just hit the block key!" to the server every time. The same goes for other inputs from you.
Every time your client sends any kind of data to the server, it's considered a "message" ...
They generally say this is "due to addons", but I don't run any and it still happened after Temporal Guard bugged out and sent me slingshotting back and forth.
ZOS should change that error wording to Booted from Server due to 'Excessive Lag'
I have had it happen to me, and I am on console. Always when lag is really bad.
I think that's essentially what it is. At a guess, when it's laggy you're spamming buttons which all get added to the queue, then when the server finally wakes up it gets this flood of stuff to deal with and boots you.
For help with troubleshooting Error 318 please see our FAQ here. This help article will go over possible causes and steps you can take to get further assistance.