How do you assign a retainer a JOB?

[Niwashi]

It's simply based off the number of posts that you've made.

I thought the number of "likes" we've given and received also figured into it somehow. (I'm not really sure, though.)

I see. What's the significance of the yellow & white badges & red & blue ribbons?

Judging by the names of the images, it seems that a gold medal / red ribbon is worth five of the silver medals / blue ribbons, though I'm not too sure just how much posting activity each "post rank" refers to.