Quest has an option to disable the command line. Why would you do that? How would you do that?
If you do disable the command line, you need to allow the player to do everything via links and the panes on the right. Quest already does the basics. You have the directions in the compass rose, and TAKE, DROP and LOOK AT for objects. You need to ensure all your objects have a full range of verbs.
Some commands do not have an object associated, such as LOOK, LISTEN, INVENTORY and JUMP. You can get around that by adding an object to them. Put a YOURSELF object in the inventory, make sure it cannot be dropped, and add verbs to that (a better way would be for Quest to have something built-in, but that is beyond my skills).
Some commands have two objects, and this gets tricky. You need to think about these on a case-by-case basis. It may be best to split them up. Instead of ATTACK GOBLIN WITH SWORD, have an EQUIP verb for sword, and an ATTACK verb for the goblin. An alternative would be to give a menu list of options for the second object.
So why would I want to?
For the player
The downside for the player is she loses the illusion of freedom. With a command line, she starts the game under the impression she can do anything. If she can type it, she can do. Without the command line, she is restricted to a limited number of options.
But it is just the illusion of freedom. Before long, the player will find that actually she cannot eat the flower, she cannot burn the newspaper, etc. because the author has not implemented that. Disappointment ensues. Take away the command line, and the player has already accepted that you are limited in what you can do.
In interactive fiction, perhaps the biggest problem for players is "guess the word" puzzles. The author thinks it is obvious that you should TWIST STATUE QUARTER TURN, but the PLAYER cannot understand why TURN STATUE does not work. It can be a problem for verbs, for objects and for conversation topics with ask/tell.
Get rid of the command line and the problem just disappears.
For the creator
Clearly the creator has to be careful to check the verbs for each and every object (and may well want to modify the list as the player progresses throyugh the game). However, this is an advantage, as it allows the creator to quickly check that each object has an appropriate response for every verb. You do not have to worry about inappropriate verbs, they will never happen.
Further, you do not need so many items. A good text adventure should implement every object mentioned in a description, or so the experts will tell you. If the room description mentions a table and a window, you need to implement them, just in case a player one day decides to look at them. Perhaps 95% of players will never see it, but the other 5% will complain if it is not there.
Take away the command line, and you can just forget about those scenery items.
So what do you think? Ready to disable the command line?