One of the unfortunate consequences of using a popular bulletin board system is that over time, spammers adopt it. Here’s one coming back to reply to its own post to make the spam link visible again after I flagged the initial one, removing its visibility.
In general Discourse does a pretty good job of automatically moderating new users if it reckons they’ve just pasted in a load of text. The downside is it often catches new posters who paste in an error message. In some cases it’s impossible to tell whether a new user’s first post is genuine or an attempt to become “approved” so they can follow-up with spam posts.
Just continue reporting spam posts, hopefully it remains under control.