I think you should let them write the letters the way they think letters should be written. It's a bit insulting to the admissions committee to think that they don't understand differences in cultures/norms or whatever you want to call it.
For example, I remember asking a professor at my university (University of Pennsylvania) about how cheesy or not cheesy my statement of purpose should be. He said that as an American student to keep it pretty real, with maybe like one cheesy line or statement. He talked about how a lot of the essays they get from China and other international students is all like "physics is love. physics is life" and "physics is like a box of chocolates" and "I knew I wanted to do physics ever since I was 3 months old" (ok, maybe not that extreme but you see my point) and that they understand that it's kind of the general culture at the moment to do that where they are from so they just let it slide for them. But I was told to not do that, and just kept it more real as an American student.
In other words, professors that are part of their admissions committees are smart people that are aware of all the differences depending on where you come from and take all that into account. I'm sure they have seen many recommendations from all over the world and know what kind of style to expect from different parts. I'd say just let your recommenders write the way they have been taught how to write.
Last edited by throwawayhehexD
on Tue Nov 29, 2016 1:49 am, edited 1 time in total.