We’re breaking down the barriers between you and your audience. When someone reads an article on your site and wants to comment, they can now use one of their existing social networking accounts to post a comment. No longer do they need to create yet another account and profile.
Since it is a large change, we are making Jetpack Comments opt-in. To activate it, just visit the Jetpack menu on your Dashboard and click the Activate button inside the Jetpack Comments box.
When activated, Jetpack Comments takes the place of your theme’s comment form in this nifty, sleek form:
To leave a comment, just click in the box and start typing.
After a visitor has written a comment, they will have several ways to identify themselves. A visitor can leave a comment as a guest¹, or they can choose to use their WordPress.com, Twitter, or Facebook account. For example:
You can also change the “Leave a Reply” heading and the color scheme of the Jetpack Comments form under the Settings → Discussion menu.
If Jetpack comments are turned on, but are not working, there may be an issue with the way your theme handles comments.
To check whether the theme is the culprit, try switching to one of the default themes, like Twenty Eleven, and see whether Jetpack comments work with it (make sure that Jetpack comments are still turned on when you do this). If Jetpack comments work when using a default theme, then the issue stems from your theme.
For Jetpack Comments to work, the theme needs to be using the comment_form() function to display the comment form.
You check whether your theme uses this function by looking at your comments.php file. You’ll find this file in your theme folder. Open it in any text editor and search for “comment_form()” (without the quotes). If that text is not found, then your theme is using the old way (before WordPress version 3.0) of displaying comments.
If your theme uses the old way of displaying comments, we recommend that you contact your theme’s author about updating the theme to use the newest comment function. You can point them to the comment form Codex page in your message: http://codex.wordpress.org/Function_Reference/comment_form
Remember – you can always contact support if you need help.
¹ Guest commenting is still controlled by the options in Settings → Discussion; if you disable guest commenting, visitors will not be able to use this option in Jetpack Comments.