I have got dropped from the server because I hit the message rate limit. But I hadn't sent a single message during that play session. Should I be concerned?
This error is usually triggered by in-game error messages which are not visible, and is not actually normally related to chat! If your character has been stuck in terrain recently, that would likely be the cause, but it could also be due to a client issue or add-on errors.
The best way to resolve it in that case would be to delete, disable or update any installed add-ons, then run the repair function from your game launcher, which you can locate in the game options menu next to the news section.