In an effort to combat comment span, I have set the number of allowed links in comments to 1. So if you provide more than one link in a comment, it will be flagged for moderation.
This is in response to link farmers trying to get their links to sites. When a post (and its comments) are indexed, the link to the spammers site is indexed as well providing them with a higher page rank.
So, if you are going to comment and have to provide a link, try to use only one. More than one if fine you just have to wait a few hours before I will approve it.