The "Active overlay display" is showing a transparent background for the "Latest Comments" when the user is logged in.
with Unregistered users everything seems ok.
I´m using joomla 1.5.9
JAPurity Template
joomlacomment4.0beta2
mod_comments4.0.0alpha3
I have the module installed at my local website only. If send me an email I´ll reply with the information for your access to my local site.
Best Regards!