As a general rule, it’s not a real liturgical abuse unless it is done by the priest or encouraged by the priest for the consecration. In today’s multi-cultural world, you see lots of different gestures of personal piety and I wouldn’t worry about it.
Personally, a gesture that is already part of the Mass is a lot easier to ignore than something that is not. The sign of the cross is already part of Mass so if someone makes it during the absolution or after Communion it doesn’t bother me at all. Same thing with striking one’s breast at the elevation;it’s already part of Mass at the Confetior. It’s the gestures and movements that aren’t already part of Mass that tend to irk me (like clapping or the swoop move) but still not that big of a deal.