Suppose Anon says, "I'm going to rob a bank next Monday."
Police respond, "We will be ready there next Monday, and you will be arrested."
Anon replies, "Ah, I see! Never mind, then."
We can certainly say it's good that Anon changed their mind after being met with promises of consequences. But, in my opinion, saying something like "Anon is a fine, upstanding citizen, worthy of praise, unlike those other criminals that actually went through with it! Now that Anon understands it's bad, they'll surely never think to plan something so dastardly in the future!" is leaving reality behind. Anon has done the bare minimum, and likewise deserves the bare minimum of praise. In terms of incentive, I think such a response would only teach Anon to be sneakier, now that they've earned some trust.