[Lots of other posts trimmed...] Similar to a previous comment, and knowing one size does not fit all, I try to preface any "style points" with a fellow dancer with "it would help me if..." and then describe or show my desired interaction behavior. Puts the issue totally on me and makes it sound like I'm asking a favor of them to adjust to my needs, not correcting them -- if it leads to further good form from them generally thereafter, so much the better. I've not had a negative reaction to this since I started doing it.
BTW, for allemandes I use a connection that I picked up somewhere in my contra travels (which sounds a lot like some of he best practices described to this point). I find this to be fairly common where I dance. As a picture is worth a thousand words, here it is (note I'm torqued slightly in these due to holding the camera with the other hand for the photo -- the normal connection is neutral and unstressed but results in good weight): https://drive.google.com/file/d/0B3My2DFMxZpOb3g1MVJWSS1lOGc/edit?usp=sharing -Don
