.byuser not showing up in comments

Hello,
Thanks for your time. I am currently making a theme and testing it on 2.9.1 on xampp, so I don’t have a URL to show what exactly is going on, but I’ve included the comments css.

I am working on the comments right now, and trying to make the post author and the user comments look different. I want to use .bypostauthor and .byuser, but when I test it on the browsers, no change is made. The comments look fine, there just aren’t any of the user or author styles showing up.

Does anyone know what I’m doing wrong? Any help would be appreciated.

#respond p {
	font-size: .9em;
	}
#respond label {
	margin: 5px 0 5px 0;
	}
#comment {
	width: 100%;
	}
#commentform {
	padding: 10px;
	}
.thread-even {
	background-color:#FFFFF;
	}
.thread-odd {
	background-color:#FFFFFF;
	}
.commentlist li, #commentform input, #commentform textarea {
	font: 0.9em 'Georgia', Times New Roman, Serif;
	}
.commentlist li ul li {
	font-size: 1em;
	}
.commentlist li {
	font-weight: bold;
	border-bottom-width: 1px;
	border-bottom-style: solid;
	border-bottom-color: #990000;
	padding: 20px;
	}
.commentlist li .bypostauthor {
	color: #FFFFFF;
	background-color: #000000;
	}
.commentlist li .byuser {
	color: #330066;
	background-color: #E2ECF5;
	}
.commentlist li .avatar {
	float: right;
	border: 1px solid #eee;
	padding: 2px;
	background-color: #FFFFFF;
	}
.commentlist cite, .commentlist cite a {
	font-weight: bold;
	}
.commentlist p {
	font-weight: normal;
	line-height: 1.5em;
	text-transform: none;
	}
#commentform p {
	font-family: 'Georgia', Times New Roman, Serif;
	}
.commentmetadata {
	font-size: 0.8em;
	border-bottom-width: 1px;
	border-bottom-style: dotted;
	border-bottom-color: #00000;
	}