OK now at least we've got a link to Metawiki containing all other updated translations, but this is less visible, the notification received on Talk page may be outdated or not translated at all, or just partly translated, and there's no way to reedit all these user talk pages later after the initial post.
But couldn't we transmit these news in templates for the delivery to Wikimedia wikis ? It would allow controlling the content that all users on that wiki will receive and see, and correct it (or translate it there if this was not done) in one place, so that all local users will benefir from these corrections.
What I mean, the bot would use a different scheme for posting to the Template: namespace of that wiki : instead of adding a new section, it would create a subpage of a given main template name, and would possibly change the content of that main template to be a simple redirect to the appropriate subpage created by the bot.
Then instead of posting the full content of the news to each user talk page of that wiki, it would send just add a title for the new heading, just followed by the transclusion of the template subpage (this would also reduce the amount of wikitext posted to each talk page, meaning also less work for the Bot posting them to subscribers).
I suggest subpages, with the base template name in the language of that wiki, and the subpage named with the date. controbutors on local wikis themselves could organize these subpages in categories if needed, or would just list them by listing pages with the same common prefixes in their name, the list being generated on the main template page by a simple search for this prefix, or by other local means.
As an additional benefit, a "Fuzzybot" could then update these local templates more easily than trying to modify talk pages, once the translations have progressed on MetaWiki.
Also I wonder if your bot can post on talk pages organized with LiquidThread (but here again transcluding the template instead of the text would also help).