When editing a section in VE, "" is now included in default edit summary. Example edit: https://www.mediawiki.org/w/index.php?title=MediaWiki_1.23&diff=2427063&oldid=2285796 (it's vandalism, but nevermind that, I can reproduce on that page too).
|mediawiki/extensions/VisualEditor : master||Section editing: strip links from heading text used for edit summary|
Oh, actually, I see it for that specific page. It's because the translate stuff is deeply confusing our expectations:
So it's building the summary of the section-heading... which as far as it can tell legitimately has some text saying "" within it.
Yes, this is user mis-action by writing <translate>== Foo ==</translate> instead of == <translate>Foo</translate> == like they're meant to, but we need to work around it (until a DOM-based system for Translate comes along in the magical future).