Al Lowe (designed of Leisure Suit Larry) on ways to avoid generic and unhelpful negative feedback (You can’t do that, I don’t know what you want to do, etc) in parsers.
Essentially, he wrote a module in his games that logged the scene and action every time a beta tester tried to do something that they couldn’t (give false teeth to window) and then went through the logs and added custom and helpful messages for each of those interactions. Could be an idea for a module or at least some useful advice to people doing/seeking testing of their games.
The video is here, it is mostly about adventure point and click games, but touches on the parser, which relates to IF.
16:10 @ https://www.youtube.com/watch?v=QjPU64MiyDU