ksfkay

Thanks esmi, but these two plug-ins are more difficult solutions. Users just want to paste a URL into the comments box without all the hassle of other tools.

COMMENT IMAGE EMBEDDER by Trevor Fitzgerald
This plug-in makes a simple operation harder. It adds a button, that pulls up a dialog box for users to copy and paste URLS to. Then it proceeds to display markup (ie: [img]…[/img]) confusing the process.
http://wordpress.org/extend/plugins/wordpress-comment-images/

COMMENT-IMAGE by Satollo
Forces users to upload images, rather than simply allows them to cut and paste links into their comments.
http://wordpress.org/extend/plugins/comment-image/