It's not against voluntarist principles because this is a DAC. Your shares are property ownership. You therefore have the right and duty to express your subjective opinion of a post's value. The goal is to increase the value and profit gained from your property (the blockchain). If you are paying for a service (blogging), you have a right to say someone's wages are higher than the value they provide. Once delegation and professional curation is worked out we'll see a lot less bullshit I'm sure, but flagging is a necessary part of post appraisal.