One of the irritations with Blogger has been that if you want to leave comments on a blog that’s hosted there (and by BlogSpot), you either have to have a Blogger/BlogSpot blog yourself, or you have to leave comments anonymously, depending on how the blog owner has set his or her blog’s commenting preferences.
Now your visitors can comment without having to sign in to Blogger. They can just fill in their name and web site and post that sucker. Also, you can have comments work in a pop-up window and other cool things. I invite you to try them out. Make an evening of it if you like. Good times.
See the updated Blogger help page How do I leave comments on a blog? for details.