Explain why the specific, shallow quality of the humour in moria — rather than simply the presence of joking — is what makes it a recognisable clinical sign rather than just a cheerful personality.

Plenty of people joke frequently as part of an ordinary, engaging personality, so joking on its own cannot be a clinical sign. What marks moria out is the particular quality and context of the humour: it is shallow, hollow, or childish rather than reflecting genuine wit or warmth, it appears regardless of whether the situation is appropriate for humour, and the person seems unable to engage seriously with a topic without lapsing into it — an inability to switch the joking off when the context calls for something else. This combination of persistence, inappropriateness, and hollow quality, especially alongside other frontal signs such as disinhibition, is what separates moria from an ordinarily humorous disposition.