Show Users As List Of Two, Not Frequent Posters

Product Support
3 
/* hide all avatars */
.topic-list .posters a {
    display: none;
}

/* display first avatar in list */
.topic-list .posters a:first-of-type {
    display: inherit;
}

/* display last avatar in list */
.topic-list .posters a:last-of-type {
    display: inherit;
}

Admin, Customize, CSS/HTML