Since today, when writing a reply to a LQT page, **if you hit preview**, a prompt warns you that you're about to leave the page, which could lead to loss of your pending edits.
I've tried to proceed with the warning, and indeed the page got reloaded with ?action=submit. Hopefully, the page opens the preview on the correct message, and doesn't try to actually edit the whole page.
Until today, hitting preview performed an AJAX communication with the server and displayed the preview without reloading the page.
In fact, once I'm on the preview page (after the page got reloaded), hitting preview again performs the preview in AJAX requests, as it was being done previously.
It can be tested on [[ https://www.mediawiki.org/wiki/LiquidThreads_Test_Page?debug=true | LiquidThreads Test Page ]]
My guess is that something got broken in [[ https://www.mediawiki.org/wiki/MediaWiki_1.25/wmf23 | 1.25wmf23 ]]