If you already have the max number of comments that can display, you can restrict them by using the nth-last-child or nth-child css selectors and setting them to display: none;
Example:
/* hides the second-to-last element */
.class:nth-last-child(2){
    display:none;
}
/* hides the third element */
.class:nth-child(3){
    display:none;
}
edit: Don't do that if you only have a few comments though or things might act weird as you get more comments and you'll have to readjust