May have found the reason the spam flag count is not auto-killing spam:

This one’s for you, @cdaquila

This post was flagged by 6 people including myself as spam, but the spam flag counter has only advanced to 2.

Rest assured that even though Vanilla measures your votes at only 1/3 strength, I think each and every one of you is worth a full spam flag!

Thank you for your observation. I was wondering myself.

I noticed than when I am the 5th person marking it as spam, it disappears. Kinda cool and makes me feel quite powerful!

Galant-you are correct. Being flagger #5 is fun.