It seems VE is exposing cursorring, free editing and even slug creation inside a syntax highlighted element.
Setting high priority because, when serialising, this change is ignored and not part of the diff. Leading to loss of edits from users.
<RoanKattouw>: WTF it has typeof="mw:Extension/source" and everything
<RoanKattouw>: > ve.dm.modelRegistry.matchElement(n)
<RoanKattouw>: I think this might be due to edsanders's ModelRegistry changes, maybe?
EDIT: This actually affects all production wikis (except testwiki/www.mediawiki.org). ve.dm.MWAlienExtensionNode is never loaded (it's in the experimental module only). Probably caused by the ModelRegistry changes earlier this year (maybe a6144f31f), since it would now fallback to DivNode instead of AlienNode?