Put an 'Add comment' link at the bottom of the page.

After reading the (usually lengthy) comments on an issue, I have to scroll back up to the top to click Add Comment.

Most websites put an 'add comment' link at the bottom so it's there when you want to use it.

In a related matter, there's no indication of the 'Add Comment' access key, which is apparently 'm'. You should have a title on the link or underline the letter to indicate that.