User blog comment:DaNASCAT/Technical Update: March 21, 2016/@comment-25648422-20160321235404/@comment-126761-20160322111033

That Preview button has been on our list for a long while, but other things have simply taken precedence.

Regarding rollback - missing them out (for self-demotion) wasn't a conscious choice, they just aren't a primary group. I'll bring them up.