John flung the match into an adjacent flowerbed, a proceeding which was too much for Poirot’s feelings. He retrieved it, and buried it neatly.
This line establishes Poirot as a perfectionist with exacting standards.
Everything must be taken into account. If the fact will not fit the theory—let the theory go.
Yes, he is intelligent. But we must be more intelligent. We must be so intelligent that he does not suspect us of being intelligent at all. There, mon ami, you will be of great assistance to me.
Hastings feels really proud after hearing this; while in fact, Poirot the patronizing bastard has insulted Hastings without him even realizing that.