The list of next badges seems oddly sorted. Here's mine:
For instance, refiner should definitely sit between Explainer and Illuminator, as they form a set of badges.
Perhaps Archaeologist should be ahead of Socratic (Silver is easier than Gold? Editing easier than answering?)
Legendary is also ahead of mortarboard...I didn't spot this when my Freehand Circle Drawing tool (paint) was open.
So what determines this order?