"GIRM 43. The faithful should stand from the beginning of the Entrance chant, or while the priest approaches the altar, until the end of the Collect; for the Alleluia chant before the Gospel; while the Gospel itself is proclaimed; during the Profession of Faith and the Prayer of the Faithful; from the invitation, Orate, fraters (Pray, brethren), before the prayer over the offerings until the end of Mass, except at the places indicated below.
They should, however, sit while the readings before the Gospel and the responsorial Psalm are proclaimed and for the homily and while the Preparation of the Gifts at the Offertory is taking place; **and, as circumstances allow, they may sit or kneel **while the period of sacred silence after Communion is observed…"
The posture at that point in the Mass is 100% up to the communicant, even though the US bishops tried to mandate a standing posture after communion. Neither standing, sitting nor kneeling is any better or worse than the others – no matter what our pious egos might suggest. It one were “better” than the other two, it’s clear the Church would not allow the options except in extraordinary circumstances and that is not the case.