This is inaccurate. WScript.Sleep causes the script engine layer to hang. No events or aliases will process so long as the single-threaded script layer is frozen.
The UI layer, however, is not running entirely within the same thread, so mIRC will *seem* responsive, but it is not really.
I've seen no real world use cases where the COM WScript.Sleep alias is at all useful. If you need a delay for a set time, use a timer, there are far fewer side-effects.
