Blogger Help : What is BlogThis! ?
Oops. I gave my class a bum steer about Blogger's "Blog This!" tool today, thanks to being a little rusty about using this page. The "Blog This!" link at a the top of any Blogger weblog page (including this one, in light blue at the top center of the screen) is a way for readers to quickly link their own blogs to your site.
That certainly makes a comment-on-sites-I've-visited weblog easy to do.