Its because the first line of each post isnt getting wrapped in a paragraph tag for some reason. A quick css fix could be to assign a font-size for bbp-reply-content.
Viewing your page source shows the first paragraph in each reply is missing the opening <p> tag.
Ring any bells?
I’m not fingering that particular Dev4Press script, mind. For one thing, it doesn’t directly manipulate content other than to copy selected text for quoting purposes.
I’m just suggesting this might be an issue with a plugin, or with the interaction of two or more plugins — and you do have a few active. 😉
I can’t replicate the behaviour using WP 3.4.1 and BBPress 2.1.2 with a TwentyTen child theme, but then I don’t run any of the plugins you do.
I removed the gdbbPressTools plugin this did the trick!
Thank you aaclayton & iamzippy for your replies, much appreciated.