I've been mulling over the concept of "gratitude" with respect to KD1:
KHARISI - ΧAΡΙΣΙ - χάρισι - /'kʰa.riːsi/ - the dative plural inflection of χάρις (kháris) from χαίρω (khaîrō, “rejoice”, “take pleasure in”, “delight”) meaning “gratitude”, “favour”, “partiality”, “partisanship”, “indebtedness”, “benevolence”, “care”.
Kuria Doxa I indicates that ΧAΡΙΣΙ (or kharisi, variously translated as "gratitude", "favour", "partiality", "partisanship", "indebtendess", "benevolence", and "care") is a form of weakness. Epicurus identifies "gratitude" (kharisi) as being incompatible with the character of an animal living their best life. Kuria Doxa I seems emphatic that ΧAΡΙΣΙ (kharisi) is to be discouraged.
In nearly every other extant document, "gratitude" (expressed using forms of kharis) is encouraged as an indispensable moral practice:
In his Epistle To Menoikeus, Epicurus encourages the old to practice gratitude "so that although old [they] may stay young in good things owing to gratitude [kharin] for what has occurred." He repeats this point in Vatican Saying 17: "the old man [...] has secured the goods about which he was previously not confident by means of his secure sense of gratitude [khariti]."
In Vatican Saying 55, Epicurus seems to encourage the practice of gratitude as a remedy against depression and regret: "Misfortunes must be cured by a sense of gratitude [khariti] for what has been and the knowledge that what is past cannot be undone". Gratitude seems to be encouraged through the practice of Remembrance, exemplified by Epicurus in his final Epistle To Idomeneus as a means of managing pain.
In Vatican Saying 69, Epicurus identifies the "ingratitude [akhariston] of the soul" makes animals "greedy for unlimited variation in its lifestyle". This seems to be a consequence of failing to abide by Nature, exemplified by the failure to recognize the fact that the greatest pleasures are the most abundant, whereas the most rare luxuries always seem to instigate unnecessary stress.
In a fragment, Epicurus reinforces the aforementioned prioritization of desire. He is recorded as having said "I am grateful [kharis] to blessed Nature, because she made what is necessary easy to acquire and what is hard to acquire unnecessary" (U469).
At numerous points in De Rerum Natura, Lucertius encourages gratitude (grata) and rejects thanklessness (ingrata), echoing Epicurus' recommendations in his Epistles (found in at least Book III.931-42, III.955-60, III.1003-1010).
... given all of this, I am wondering: what is unique about the employment of kharisi in KD1 that contradicts these other usages?