I've been noticing this a lot recently: people spend a great deal of time marking their identities in various visible ways. I've spent time working on marking my identity recently, because I'm thinking of getting a new author picture of myself, and I'm trying to decide what to wear so I'll look like who I am! Writer of fantasy about Japan, and her own created worlds, and alien languages, etc...
The question of identity is complex, because none of us are all one thing. The marks of identity parallel this complexity. While something like a tattoo is difficult to remove, it can still be covered up. People typically will adjust their appearances to respond to the perceived audiences around them, and to show alignment with different social groups. When I take my kids to school I wear very basic clothes; when I go out with friends I like to do "dressy casual"; when I go to a convention I wear an outfit intended to show my imagination. I'm not the type of person to put bumper stickers on my car, but even the type of vehicle we drive can demonstrate our identity to others. The type of pen we write with; how we carry our belongings with us. The list goes on and on.
This is something to consider when you are putting together a story, creating and dressing characters and surrounding them with objects. People are very likely to care deeply about their appearance in one way or another - even to target particular groups they want to offend!
I recently put up a question on my Facebook page about what kind of jewelry otters might wear - and I was surprised and pleased at how many people gave me great ideas. At one point I was trying to decide which of the ideas I liked the most, and then I realized I could probably use more than one. Why restrict myself? Why not have otters choose various jewelry styles to reflect their personalities and preferences?
I want to add language use as one more identity marker. This includes not only choice of words and politeness strategies, but also things like tone of voice. People who have heard me speak Japanese often remark on how I use a higher tone and smaller body language when I use Japanese. I've been asked whether I do this because I have to. The answer is this: I don't have to - but mannerisms that fit with my use of English don't have the same meanings to the Japanese cultural community. In order to appear to be the same person - with the same degree of forthrightness, and the same degree of consideration for others - I need to sound different in Japanese. Simply importing my English mannerisms into Japanese would cause me to appear much more brash and rude than I actually am, and it wouldn't serve me well in making the social alliances I look for. This links back to the question of aiming our identity markers at particular social groups. Often we'll do it very deliberately, and even when we do it subconsciously, we're typically very good at it.
It's worth thinking about for whatever world or universe you happen to be writing in.