Problems with the use of GRAMMAR

Well, message previews are meaningless anyway, since they don't reflect the reality and I would just disable the previews altogether (rendering the text as-is) if it was easy to do so.

Now what comes to translated pages, they should indeed be rendered with the target language of the translation. If this is not the case, it is a bug that I need to investigate.

What comes to the third point (disregarding the language of the message), that is a issue in MediaWiki itself, and more specifically a very hard one to fix.

Tested and it works fine with translatable pages.

Yes indeed. Did you change anything for them? Else, I must have been victim of a caching issue, when I wrote the above. I'm happy that it works so well!

As to the message preview, there is a special case of preview for specific *.js and *.css pages already. Did you check it for hints hat could be useful for us at twn?

The third point is indeed hard to tackle. I've been at closely related issues for various reasons once in a while, and I believe fixing them all together in one go is easier than trying to solve them individually. My current idea is to convert every rendered string to an ordered list of tupels for internal processing, with each tupel at least having a locale (i.e. language, variant(s), script), directionality, joining behavior, and content. That would also require attaching those properties to wiki pages proper, offering an opportunity to do away with "title/xzz" hacks if a wiki chooses to do so.