I don’t think
@pointsdecorate meant that guests can report DMs. Users can report DMs they get, but guests have no DMs to report. I think they mean to say that guests can report anything they see on the public portions of the site. I forget if there is a report option for guests or not, but there is a
public contact page at the bottom of the site. You don’t need an account (that is, you can be a guest) and report a post to staff through an email. One just has to include a direct link to the offending post.