Features:

Clientside - the features a entirely clientside, and will work on any server. Does nothing, if installed on a server.
Toggleable - with built in commands, you can easily turn it on and off as needed. (.clearspam help)
Removes Spam - by looking through previously sent messages, the mod determines if the message is a duplicate, and makes sure that only one of each message is visible at a given time, cleaning up the chat.

Commands:

.clearspam toggle - toggles the features of the mod on or off. It is turned on by default, each time you start the game.

.clearspam on/off - toggles the features either on or off.

.clearspam reset - resets the spam counters.

.clearspam help - displays this list of commands.

Notes:

The mod was requested by user marcocorriero. It is inspired by an AntiSpam feature in the Wurst client, which I didn't know of, but marcocorriero explained it to me. I coded the mod from scratch, and the mod does not use any code from the Wurst client.