The Hide dialog operation is just weird. If I enter a reason in the dialog and then click [Hide], I'm prompted

"This page is asking you to confirm that you want to leave - data you have entered may not be saved."

if I confirm [Leave page] then the page *issues* a Post request to http://en.wikipedia.beta.wmflabs.org/w/index.php?title=Topic:S3dqqucjtbymepci&action=moderate-topic&topic_moderationState=hide . This replaces the Flow board with the topic alone showing "This topic was hidden by Spage beta."

in other words the page is not making an AJAX API request, it's visiting this URL as if JavaScript is disabled. Hence I guess the prompt about "data you have entered may not be saved."

I don't get this behavior if I log in to beta labs in a private window, nor do I get it in Chromium. I was getting it on regular page and with ?debug=1. I hope it's an unreproducible cosmic ray.