Unless it spawned a bat-signal that alerted Kaguya of posts that break the rules when he's off-line, then i don't think a report feature is necessary right now
spam attacks are, well, quite apparent. Furthermore, even on /b/ posts are made at a rate where there's a lot of time for it to be delt with. That holds true without considering that the userbase tends to call out anything that goes against the balance of the echosystem
A report feature will only be needed when rule-breaking posts are frequent and abundant. It is true that a huge influx of users might threaten to make the aformentioned statement true, but only if we first neglect those kind of posts during the current stage of the site