Change Author extension
I've found this extension yesterday and looked at some of its translations and I noticed something there: The extension currently uses different messages when you change only one author and when you change multiple authors (Changeauthor-changeauthors-multi, Changeauthor-explanation-multi, Changeauthor-changeauthors-single and Changeauthor-explanation-single. I don't think that should be done, because plural rules differ from language to language. When the plural in English is used, some languages might still be at the singular. Also, in the messages I think singular/plural actually doesn't matter at all, the people will get it like that. Thus, I'd solely use Changeauthor-explanation-multi and Changeauthor-changeauthors-multi when changing an author (and remove plural there).
Independent from the first concern, Changeauthor-explanation-multi and Changeauthor-explanation-single make hard coded button label reference, which should be replaced with int:
Changeauthor-comment ("Comment:
") looks like something where you write why you changed the author and such fields are usually called "reason".
There are two different forms in this extension. One changes the author of a specific revision (so everything is always singular there), while the other form allows you to change the authors of each revision of a specific page (usually multiple revisions, possibly just one if the page only has one revision). That's why there are separate sets of messages, and that's why the -multi messages are pluralized. So it is actually possible to hit the -multi message in the singular case, you'd just have to find a page with a single revision in its history and go to the form to change the authors of all revisions of that page.
I hope that makes sense?