In several of the groups I co-admin, laugh emoji in response to a serious post is considered a form of bullying, and is against the rules of the group.
Sometimes we find out that a person has hit the laugh emoji by mistake. But sometimes we find out the person is a troll or just not a fit for the group.
As I see it: Our groups need to be safe spaces as we navigate fear, grief, and other difficult emotions; and as we get vulnerable sharing our deepest concerns like underpreparedness and collapse. Mockery makes a space unsafe.