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I am afraid that the pleasantness of an employment does not always evince its propriety.
— Jane Austen · Sense and Sensibility

Behind the line May contain spoilers.
Our reading
An editorial interpretation.
The speaker politely distinguishes the pleasure of an activity from its propriety. Enjoyment, in this view, does not establish that something is appropriate. The careful wording turns a possible objection into a restrained caution, separating what feels pleasant from what can be justified.
Context reviewed