Okay, I've been wondering this for a while, I've banned one of my keys on Dream Daemon from my own game, I filled in the reason which is there to remind you why they were banned, but The message(optional) what is that for? I've entered a message and when I tried logging in my own game it just says Access Denied I'm not sure what that really is for, Anyone want to clear this up for me why its there or HOW they can see the message?
Wow so no one knows o.O how disappointing
I think it is pretty obvious, the message is shown to them when they try to log on, the reason is for you so that you know why they are banned.

Reason: PERM BAN - Ripping
Message: You are banned from the game.
it doesn't work mr.Quaddw
Read the entry for IsBanned() in the DM Reference. If I recall correctly, it hints at how to get access to the "reason" string via DM. (I assume you're meant to code in the message display yourself.)

This might be inaccurate. I haven't played with the ban system enough to understand it completely. Hopefully it's at least a lead.
That may be but in BYOND 4.07 and below the message will display to people trying to login.
In BYOND 3.5 and below there were pagerbans, which had the same thing: a "desc" param which displayed that message to the player upon denying access.

When you tried to login, it would give that message, followed by "Access denied."

I can only guess that the 4.0 DreamDaemon attempts to emulate this behavior. But the Options and Messages window appearantly doesn't output that string any longer.

-- Data
This should be reported then, sorry for the late reply.