Your instructable became popular ... again? Answered
Maybe you could change the "your x became y" message to be different for each tier? The email seems to be identical each time the popularity rises, and that just feels like spam.
I don't really get the badges, either. I thought at first it worked like the badges on stackoverflow. Instead of simply telling someone "your thing is not crud" you could award them a badge for being ++good, and have different badges for each tier. Naturally, the email would have to be different for each badge, etc. You could further motivate people by letting folks see each other's badge list. Almost any action a person makes could be a badge - even a badge for having every other badge!
I'm just thinking... young people. play too many games. they get game mechanics. so reward them in a similar way, and they'll feel like contributing more. work that pokemon "gotta catch 'em all" addiction.