Hook to edit an column on comments screen?

At the moment I’m doing

add_filter("manage_edit-comments_columns", function($columns) {
        unset($columns["author"]);
        $columns_one = array_slice($columns,0,1);
        $columns_two = array_slice($columns,1);
        $columns_one["user"] = "User";
        $columns = $columns_one + $columns_two;
        return $columns;
    });

add_filter( 'manage_comments_custom_column', function($column, $column_id) {
        echo "Test";
    },10, 2 );

Is there a way to just edit the author column instead of removing and creating my own?

There is no filter for this column. So answer is ‘No’.

WP_List_Table search for method column_{something} inside class of Lister. Comments List class has column_author. So kill this column, and create filter as you do now.