ChatCo is a simple chat plugin which has the following features:

Players can customize their chat message using various prefixes. As an example putting an '>' before a chat message will turn the text green (greentext). (Note: Does not change the color of player names).
Players can whisper other players (defaults to a purple color).
Players can ignore another player (works for both world and whisper chat). Ignore lists are persistent between logins. Players can also unignore a previously ignored player.
Allows for a cusomizable spoiler text system (who wants to ruin the walking dead for everyone?).
Players can toggle chat on/off.
Full permission support so that you can limit who has access to what colors / features.
Allows the administrator to log whispers between players.

Popular servers known (or thought) to be running this plugin:

9b9t.com
Anarchy.pw
2b2t.net

ADMINISTRATIVE COMMANDS (only console input is accepted):

Every single command goes by the format "chatco component e/d" where 'e' enables and 'd' disables, e.g. typing "chatco whisperlog e" in the console will enable whisperlogging. You will have to reload the plugin in order to make most of the changes take effect.

Components:

spoilers
whispers
newcommands
whisperlog

Player Commands:

/ignore
/ignorelist
/togglechat
/toggletells

Whisper Related Player Commands:

/tell
/pm
/w
/msg
/t
/whisper
/r
/reply

Legend:

spoilers - enables or disables spoilers, is disabled by default.
whispers - enables or disables whisper changes, is enabled by default.
newcommands - enables or disables new whisper commands, is enabled by default.
whisperlog - enables or disables whisper logging (whisper logs are saved in /ChatCo/whisperlog.txt), is disabled by default.
/ignore <player> - ignores or un-ignores the player.
/ignorelist - prints all ignored players.
/togglechat - disables regular chatting for the player - NOT PERSISTENT.
/toggletells - disables tells for the player - NOT PERSISTENT,
/r and /reply - replies to the last person who sent you a whisper this session.

Config

Color codes and prefixes can be disabled by replacing the contents of "" with "!#" e.g. Green: "!#".
Usage of color codes and prefixes can be restricted by using permissions.
You can customize the appearance of whispers.
More info

Examples:

Turn chat off/on with /togglechat.
Write > at the start of a message for greentext.
Write [ SPOILER]text[ /SPOILER] to make a spoiler.
Write /show spoiler [1-5] to view spoilers.

Planned Features:

Fully Async Chat
Groups?
Customizeable Death Messages
Last time a player was seen online?

Minecraft Versions (Confirmed Working):

1.11.2
1.11.0
1.10
1.9
1.8