Oh hey, time for this extension to be useful!
This is exactly what Parser Overrides are meant for. If you put your response in an “after reading a command” rule, then you’re bypassing Inform’s whole action machinery and making it difficult to tweak the responses in different circumstances, but if you rewrite the command, then you can end up with odd bugs like “GO WEST. INCINERATE POTATO” turning into “THINK ABOUT GO WEST. INCINERATE POTATO”.
A parser override rule:
repeat through the Table of Concepts:
if the player's command includes the topic entry:
override thinking about overridden topic "[the matched text]".
Now any command including “potato” will be parsed into the action “thinking about ‘potato’”.