It seems that Jews ought to be distinguishable from the other nations. There are many accounts, especially from insular communities, of people changing little details in their dress just to be different from gentiles. But what if a gentile likes the jewish look? I'm not talking about tzitzit but about practices of customary dress. For example, wearing a kippah at all times, a rekel with gartel and black hat, or a kaftan yerushalmi.
I've seen in this site one explanation for Jews not to sell garments with tzitzit for gentiles because the gentile could be considered a jew and could end up killing a Jew. Well, many Jews today wear tzitzit under another garment, and the examples cited before were all common among gentiles at a time (or a very similar version at least). Would a gentile be liable if he looks like a Jew?