I see mention in the what's new page of a customized sort order for certain functions, including {{action}}. I can't find the syntax and which functions it applies to. Am I missing something, or did that get rolled back?

I think it still works. Here's the old reply Matt sent me in 2012:

The options are abc, updated, created, popular and priority. Each can be sufficed by either > or < for ascending or descending sort order. The default is ascending. Multiple options can be passed, e.g. abc>,popular< for sorted alphabetically then by the most popular.