Dec 7 2020
Apparently the content still exists in DB because MW considered my edit to MediaWiki:Recentchanges-helppage null edit when I added exactly the same content it used to have. Now the content is shown on the page, but still not in the edit window. (and the message doesn't change the help link while it should)
Oct 20 2020
This seems to only affect certain pages, specifically those edited between July and last week, as I was able to edit my user page and a template today.
Oct 14 2020
Oct 6 2020
Parsoid is now bundled with MediaWiki 1.35, as is VisualEditor. I suppose that will make it significantly easier to install.
Jun 28 2020
Special pages seem to be unaffected by this. However, it also seems that some article pages are missing, for example, I noticed that in fi.starwars Taistelu Ord Mantellissa or Star Wars (Yhtyneet Kuvalehdet) are not included in search suggestions.
For the record, Special:MyWikis throws the same error.
Jun 25 2020
Okay, apparently https://phabricator.wikimedia.org/rMW2d33abad9280f338e625768a408b067763a3064e should fix this. Not sure why this hasn't been backported to REL1_34 branch...
Jun 11 2020
May 1 2020
Apr 24 2020
Dec 26 2019
Mar 5 2019
Jul 12 2016
Jul 10 2016
In addition to Monaco, "More Wikis" is also broken in Nimbus.