About [[MediaWiki:Changeauthor-explanation-single/en]] and [[MediaWiki:Changeauthor-explanation-multi/en]]

I don't quite follow, how should it be using int exactly?

Never mind, I get it now. This is easy for -single, but not so easy for -multi because it's a parameterized message. Instead, should I reword the message to just say something like "the button below" without quoting the button's caption?

 :) Yes, this is a possible and pragmatic alternative approach. I believe this would be better than the existing message since this definitively helps avoiding discrepancies between the translations.

However, you must be sure that's actually the position in all cases.