The script, that makes all your messages appeared in different font. It works on 6.0 PTR Realms.
You can download the addon or try it with this in-game command:
/run ascm=SendChatMessage;SendChatMessage=function(x,...) ascm(x.."㒫",...) end
To reverse it type /reload or /run SendChatMessage = ascm;
Addon adds a japanese symbol to your messages, which is invisible unless you have special fonts installed. A message containing any of japanese symbols is displayed differently than normal messages, it looks more cool, see it yourself!
To answer the question whether or not is this banable I would like to quote GMs 'Everything inside addon folder that is not executable itself is legal.'
I don't know if different displaying of letters is intended or not, perhaps this issue will be adressed in the future.