I tested template translation after the deployment on Thursday December 1 2016.
I couldn't publish a translation from Hebrew to Spanish or French. I repeatedly got "docserver-http: HTTP 400".
It worked correctly when translating from English or Catalan into Spanish.
I tried the article "מגדל שלום מאיר" and several others.
The title of the article in the target wiki is "Usuario:Amire80/Migdal Shalom 12-5-1" (in the user namespace, "Usuario").
I tried this again today December 5 at 09:39 AM UTC.
I received several other complaints about it. One on Talk:CX: https://www.mediawiki.org/wiki/Topic:Tgh3cf65cf0upl26. It says that the user could not translate H. M. S. Richards to Spanish, and this means that it is not unique to Hebrew. I received a couple of other complaints over email.
I am able to reproduce this and it is independent of language or title. I got the smallest HTML snippet that can cause the parsing system failure
<span about="#mwt5" class="mw-ref" id="cxcite_ref-2" rel="dc:references" typeof="mw:Transclusion mw:Extension/ref"></span>
Just paste this html in HTML field of https://ml.wikipedia.org/api/rest_v1/#!/Transforms/post_transform_html_to_wikitext_title_revision - 400 is guaranteed.
This HTML snippet was output of Yandex MT. data-mw is missing.
I also found that removing mw:Transclusion from typeof attribute makes the parser working
<span about="#mwt5" class="mw-ref" id="cxcite_ref-2" rel="dc:references" typeof="mw:Extension/ref"></span>
That also mean the following snippet is enough to create 400
<span typeof="mw:Transclusion"></span>
And this is expected behavior from parsoid https://github.com/wikimedia/parsoid/blob/master/tests/mocha/api.js#L1231
So from CX, we should avoid creating HTML without data-mw if typeof=mw:Transclusion
Change 325520 had a related patch set uploaded (by Santhosh):
For unadapted inline templates, ensure data-mw even after MT
Change 325520 merged by jenkins-bot:
For unadapted inline templates, ensure data-mw even after MT