If you look at the top left of any post you'll see some icons. These are the post options:
Wherever you see this icon: you can create a comment. Click it and you'll see something like this:
As with post creation, Blog uses Sakai's built-in rich text editor for editing comments and this allows fully formatted text, embedded images and templated layouts. Creating a comment is easy. Just enter the comment and click 'Save'.
Here's how the comment looks after creation.