Other plugins can hook into Chatter. They can use the RegisterPlugin function using the cPluginManager:CallPlugin function
You use the RegisterPlugin(Tag, PluginObject, FunctionName) function. Here is an example:

--This goes in the OnPluginsLoaded function:
cPluginManager:CallPlugin("Chatter", "RegisterPlugin", "Faction", cPluginManager:Get():GetCurrentPlugin():GetName(), "MessageFunction")

--And this is an example of how the MessageFunction could look like:
function MessageFunction(a_Player)
      local PlayerName = a_Player:GetName()
      if Faction[PlayerName]~= nil then
            return Faction[PlayerName]
      else
            return "Fairy Tail"
      end
end

In this case when Chatter finds "{FACTION}" in the prefix it calls the given function with the player object as parameter. The given function should then return a string that shall replace "{FACTION}".

Note that Chatter automaticly adds the braces around the tag and capitalizes it.