If you 'vouch' or 'flag' things the mods don't approve of, it gets disabled on your account.

Confirmed in private conversation with dang [1], he restored it after I promised to behave, and now it stopped working again as I didn't properly toe the line.

Quite hypocritical to give power to the user with the tacit expectation that you share the same opinions and political bent as the moderation team.

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1: quote: "I'm afraid we took vouching privileges away from your account because you vouched for too many comments that were unsubstantive and/or flamebait and/or otherwise broke the site guidelines"