Well it has been over 6 years and I still see the same behavior.
If I start logged in and use a client to connect and switch to the login window, the console switches but I remain in my session. However, the screen does not go back off as long as I am doing something in the VNC session.
If I start at the login screen or logged in as another user and the display is asleep, the screen wakes up for almost exactly one second every time I type a key or move the mouse and then goes back to sleep! I can’t imagine it is that great on the display circuitry to have constant wake/sleep on the display like this, and in any case this is even worse than the display staying awake - imagine this happening at night in an office and attracting unwanted attention such as security.
It also isn’t great to have the display waking up at all - it can be a great security risk and/or annoyance as it alerts others that somebody is doing something on the machine. In some situations this is unacceptable. Other solutions such as finding ways to forcibly turn off the display won’t work either in situations where another user might be logged in, in which case we don’t want to disturb them (by forcing the display off) or might not be (in which case they might not restore the display settings when they leave the computer).
I don’t really understand why the screen is coming on at all; I was under the impression that by setting a non-standard port such as 5901 that a virtual session (like a Terminal Services thing) is being created separate from the session that the stock VNC server under OS X would create.
Any pointers on how to achieve this are appreciated, in the event that this problem has actually been solved since this thread was created. If not, I hope this will be fixed soon as this problem greatly limits the circumstances in which remote access to the machine is useful to me.