That forum is for Forum announcements.
Igor makes nginx announcements and they are posted to the mailing list
and its integrated forum. If and when another mailing list is created
then it will be included as a separate forum along with an RSS feed.
If you would like an nginx annoucements forum before then I will happily
create it and you can maintain it. Let me know off list - preferably by
using the “Site Suggestions” forum.