I have just tested the blog and here is what I did to leave a comment.
Click on comments under the post you want to comment on
typed comment in the text box and used bold tags text bold to bold some of the text.
Filled in word verification
Chose an identity - other - and called myself m
Follow this and you should'nt go wrong.
If you want to make posts you need to ask me and if I agree I will set it up for you.
Give it a go - comment!