I finally managed today to activate both speech and text in space Quest IV talkie version using the instructions found at
www.spacequest.net (that is, pressing space when the narrator starts talking at the beggining of the intro and skipping it). I noticed then that when you use the main menu, it says "Both Speech and Text", and that makes me thing this is an option that was initially programmed but never made it into the game, for any strange reason.
So my question is, wouldn't it be possible to enable that option under the game, given it is already available but disabled, using reverse engineering or something?