delete: .userOnline {...} and .userOnline span {...}
add:
    .userOnline
    {
        font-weight: bold;
        font-size: 10px;
        color: @contentBackground;
        background: @primaryLight url('@imagePath/xenforo/gradients/category-23px-light.png') repeat-x top;
        padding: 1px 5px;
        margin: -5px -5px 5px -5px;
        border: 1px solid @primaryLight;
        border-radius: 3px;
        border-top-right-radius: 0px;
        border-top-left-radius: 0px;
        display: block;
        float: inherit;
        position: relative;
        box-shadow: 0px 1px 3px rgba(0,0,0, 0.25);
    }
        .userOnline .firstSpan
        {
            background-color: @primaryLight;
            border-top-right-radius: 3px;
            position: absolute;
            top: -4px;
            right: -1px;
            width: 5px;
            height: 4px;
        }
        .userOnline .secondSpan
        {
            background-color: @primaryLight;
            border-top-left-radius: 3px;
            position: absolute;
            top: -4px;
            left: -1px;
            width: 5px;
            height: 4px;
        }