It’s a nice touch to be able to quickly identify the original post author or site owner comments. I think the easiest way to achieve this is by styling the background.

If you search the web you will find plenty of plugins giving you many options with your comments. A plugin to style author/owner comments is not necessary with WordPress 2.7+ as wp_list_comments() adds a bypostauthor class. All you need to do is add the following to your stylesheet:

.bypostauthor {
background-color: #E7F8FB !important;
}


Here is a screenshot of what is looks like:

Comment highlight in action.