The parser error "That noun did not make sense in this context" arises instead of "You can't see any such thing" when the player uses a command that could apply to any item in the game -- that is, a command such as
…and so on. The idea here is that "You can't see any such thing" isn't a sensible rejoinder when the player doesn't really need to be able to see the object.
Nonetheless, "That noun did not make sense…" is itself a fairly dry and uninformative response, and we may want to override it to something more appropriate for the specific kind of context in which it might appear. For instance:
Test me with "discuss Elvis / discuss Kennedy / discuss chocolate / discuss narratology vs ludology debate".
After about 2 AM, no one is listening anyway, so you can more or less make up whatever you like to fill the airwaves.
> discuss elvis
You babble for a while about your hatred of Elvis.
> discuss kennedy
You babble for a while about your passionate devotion to John F Kennedy.
> discuss chocolate
You babble for a while about your hatred of single-origin chocolate.
> discuss narratology vs ludology debate
For once, you're at a loss for anything to say.
Note that this solution works as simply as it does because we only have one command in the game that can apply to an "[any]" token. If we had several, we'd need to distinguish between the parser error attached to "discuss" and the parser error attached to "go to" (for instance). In that case, we might instead write something like