From 1.10 to 1.11

Comment highlighting

If your theme is using the file views/default/css/elements/components.php, you must add the following style definitions in it to enable highlighting for comments and discussion replies:

.elgg-comments .elgg-state-highlight {
        -webkit-animation: comment-highlight 5s;
        animation: comment-highlight 5s;
}
@-webkit-keyframes comment-highlight {
        from {background: #dff2ff;}
        to {background: white;}
}
@keyframes comment-highlight {
        from {background: #dff2ff;}
        to {background: white;}
}