The component is great.
I have found following bugs while doing some research. I am using XAMPP local server environment.
1. E-mail field should only allow e-mail IDs (i.e email@example.com) Currently it allows anything in the text field for non registered users.
2. RSS Feed - RSS feed for the comment should only show feeds for the specific article comments. Currently it shows all the comments.
3.Should be able to add text for Terms & Conditions for posting comment.
4. Captcha image - It shows uppercase and lowercase characters and numbers but works even if you input only lowercase letters + numbers. It should be case sensitive.
5. Reply to the comments gets indented and goes out of boundries. It would be great if there is some other layout for replies.
6. This Bug Report kind of form would be really good (Image and File attach and Preview, etc. really good).
Sorry for giving too much suggestions. I tried to teak the things (look at other comonent and then back to Joomla Comment) but unfortunately I don't know PHP, MY SQL or JAVA Script.
I don't know how much effort does this takes. I don't know if I could be of any help (Know bit of CSS and yes I can test the componet for you). Please let me know if I can help you.
Lets take Joomla Comment to great heights.
Salute to Joomla Comment developers.