Most of the time I do like to get the visual feedback.
However I must say that sometimes when dealing with large number of data being echoed (Twitch context?), echoing all the lines as a debug makes mIRC take much more time than if the the window were hidden, and in this case I'd want to get mIRC to only display once the script finish. An option to enabled this in alt + o, with a command to toggle it, would be welcome. "/fastupd on" and "/fastupd off" once you are done debugging, that would be really nice for me.
