Earlier quoted context omitted.
> For example if spammers find out which sites are banned then they just post other ones. I don't think that makes sense. The supposed spammers can just try looking up whether their submissions show up or not when not logged in.
That also requires additional effort on the spammers’ part. Increasing cost of attacks is an effective defense strategy.
Even Cory Doctorow made this case in "Como is Infosec" [1].
The only problem with Cory's argument is, he points people to the SC Principles [2]. The SCP contain exceptions for not notifying about "spam, phishing or malware." But anything can be considered spam, and transparency-with-exceptions has always been platforms' position. They've always argued they can secretly remove content when it amounts to "spam." Nobody has challenged them on that point. The reality is, platforms that use secretive moderation lend themselves to spammers.
[1] https://doctorow.medium.com/como-is-infosec-307f87004563