User blog comment:DaNASCAT/Technical Update: April 6, 2016/@comment-1251315-20160406203451/@comment-1251315-20160407141019

The issue with null editing only started yesterday. Before that, they were null editing just fine. I tested with a lengthy article (about 250,000 bytes) on another wiki and it went fine, though was slower than usual.

The issue seems to be specific with wiki's using SMW, as Yu-Gi-Oh wiki was having similar issues. I'll ask a sysop to investigate (though tbh, these wiki's should probably be ditching SMW anyway in favour of simple DPL lists).