There is a mailing list for SWI-Prolog specific issues. This list is used for announcements as well as questions and discussion amoung users. On average, traffic is 5-10 messages per day.
The mailinglist is kindly hosted by the University of Bonn using the Mailman list software. You can manage your subscription using this web-page. To post new messages, send mail to mailto:email@example.com. The list is archived.
Bugs are best reported to and tracked through the Bugzilla system. This internet based tool provides a structured way to enter, track and find bugs and their patches.