I like YouTube, but I abhor asinine YouTube comments. This wee bit of CSS neatly excises the comments section from each YouTube page I visit:
div#commentsDiv {
display: none;
}
To use this with Safari, save the code in a text file and select it with Safari→Preferences→Advanced→Style Sheet→Other. It may work with other browsers, too.
Of course, this will hide any div identified as commentsDiv that your browser happens to encounter, not just those found at YouTube. I don’t know if it is possible to restrict user CSS rules to a specific domain.
Update: Firefox and Camino users can use this version to ensure that only YouTube pages are affected:
@-moz-document domain(youtube.com) {
div#commentsDiv {
display: none;
}
}
Save as userContent.css in ~/Library/Application Support/Camino/chrome/, or the corresponding profile subdirectory for Firefox.