Interesting topic since this is something I have actually thought about for many many years.
I am not really that keen on discussing my roleplay, since I am firmly in the "find out IC" -camp. However, clothing is something that
would be obvious IC, isn't it? So I quess it's not much of a problem.
I always thought Tara actually wore amarrian robes among other things, men's kind too, with the hood over her eyes and the works. Also the tattoo on her cheek, well, that's the best the char generator let's me do at the moment. Being a caldari is a complete non-issue for her, surely it would not limit her choice of clothing, tattoos, make-up, jewelry etc.
So in my opinion, players really should be able to choose. There are reasons other than loyalty or even vanity to wear things. What breaks immersion to me is not being able to smear an amarrian robe or minmatar tattoo by wearing it in spite because
I can. Only of course, I can't.
I do see the point from people disagreeing, though, and they are right, too. It is a matter of choice, as things often are, with no clear right answer in my opinion.