[tdrp]

As a user I don't like it but as an app/website provider, it significantly delays spammers, giving them the illusion that what they're doing is working so they should just maintain the status quo.

If instead you outright ban them, they adjust or learn about your anti-spam algorithms and just keep going.

[tomcam]

Wonder if one answer would be to move potential spam, etc. to a separate-but-equal area. So if you're in /r/Politics and start advertising your get-rich-quick scheme your post is moved to /r/PoliticsSandbox.

[nkozyra]

That removes the "shadow," unless you present only to the submitter that the content is in the intended space.