Discourse.haskell.org is the official discussion forum for the Haskell programming language community. It's run under the well-established haskell.org domain, which carries decades of reputation in the open-source world. For a community site, it does a lot right: the connection is encrypted, security headers are in place, and the site clearly lists an about page, contact info, and even a privacy policy. That's more than many forums bother with.
What gives us slight pause is the lack of any record in the Wayback Machine. That doesn't mean the site is fake—it just means this particular subdomain is probably quite new or hasn't been crawled. Given that the parent domain is a trusted pillar of the Haskell ecosystem, that's a minor concern rather than a red flag.
If you're looking for discourse.haskell.org reviews, you'll mostly find discussions about Haskell itself rather than the site's trustworthiness. So is discourse.haskell.org a scam? No—the evidence points to a legitimate community forum. Just be aware that it's a relatively fresh setup, so treat it like any new online space: use common sense, don't share sensitive credentials, and enjoy the conversation.