Please test my plugin

Hi All,
I have created a plugin to allow users to comment on wordpress sites.
Please have a look at it and tell me what you think, as users can completely alter the look via the stylesheet and the function, if they code PHP, I’m not too concerned about these, mainly about whether or not it can be hacked, especially if anyone can see the code. I need to ensure that is has a secure system to it.
All comments would be greatly appreciated,
Thanks,
Sephers.

http://wordpress.org/extend/plugins/simplecomments/