People
Nothing is more deceitful than the appearance of humility. It is often only carelessness of opinion, and sometimes an indirect boast.
— Jane Austen

Behind the line May contain spoilers.
Our reading
An editorial interpretation.
The warning separates looking humble from being sincere. What seems modest may reflect an opinion offered carelessly, or it may be a boast delivered indirectly. The sharp opening invites suspicion of appearances: a self-effacing manner does not, by itself, settle what lies behind it.
Context reviewed