Why is wearing/not wearing a hakama even an issue? Isn't it proper etiquette for a visitor to simply abide by the dojo's rules, and *not* try to impose what *you* do at your home dojo? If I recall correctly, some Yoshikan aikidoka don't wear the hakama until sandan (someone please correct me if I'm wrong!)
At my dojo, only blackbelts wear a hakama; everyone else wears a white belt. This other dojo I visited, the instructor asked me to wear a hakama (I have one for Iaido), since his students start wearing hakama when they reach 3rd kyu. I didn't wear it the first time - and *everyone* tried correcting my technique, though I was a "higher kyu". The next visit I wore my hakama, and their treatment was *much* different. Kinda interesting how differently I was treated, because I wore a skirt.
Seriously, though...wearing a hakama usually *does* imply a certain level of "skill". There is a danger in this assumption, because since different dojos have different rules regarding the hakama (e.g., wearing one from the beginning, at 5th kyu, 3rd kyu, etc), this could cause some confusion at seminars. Of course folks *should* be somewhat cognizant of uke's skill level - regardless if uke is wearing a hakama or not - and *not* immediately throw someone through the mat. I worked with a couple older women (both black belts) at a seminar last fall, and both admonished me for trying to throw them "too hard". I also trained with a number of hakama-wearing students - who clearly were *not* blackbelts and kept deferring to me (maybe because I looked like I knew what I was doing - lol).