Quote from Jim on September 21, 2023, 7:07 am

Put the desired code in your theme’s style.css file.

If you want the space for avatar to remain after it disappears:

div.forum-poster div.forum-poster-avatar {
visibility: hidden;
}

If want the space to disappear also:

div.forum-poster div.forum-poster-avatar {
display: none;
}