Heeeeey, that's a bug with the visual comment editor in the chosen design (1301). I have forwarded the issue to the dev team.
The text is visible if you switch to BB codes (the BB button in the top right corner of the comment editor). So you can disable the visual comment editor till the issue is fixed: Control Panel > Settings > Common settings > Do not use the visual comment editor.
I'm not active on the forum anymore. Please contact other forum staff.
One more thing; I set it so that guests can reply to comments on articles. How do I remove the email field so that they just need to enter the name, captcha code and the comment? I know the email is optional, but I'd rather not have it there.