Irina never lets anyone share her drink. Food, whatever, but not drink. She even carries a cup on her belt for when people are passing a bottle around, so she can partake without drinking from the bottle directly. She believes that to share a drink with someone is to know their secrets, so her familia considers the sharing of drinks to be a very intimate act. I can count on two hands the number of people she's EVER shared a drink with, and four of them are direct siblings. I came up with this quirk after having Yom Kippur break-the-fast with some Argentinian extended family, one of whom ran out of water but declined to drink from my class by noting "I don't want to know your secrets". I never got to ask what she meant, but the exchange stayed with me and morphed into one of Irina's defining traits. It's also spawned some ridiculous roleplay, like people stealing Irina's cup and pretending to drink from it just to rile her up (it works), or Irina having to snatch her cup out of a Baroness's hands because the latter didn't know it was a Thing (sorry Ezri!).
Nadarin didn't speak at all for the first couple years I played her. She still pretty much never speaks above a murmur, unless it's yelling to someone in battle. She used to communicate mostly by writing in her little book and showing the words to people, but her best friend Vry was a Hastur Volg (Barbarian) who couldn't read until recently and so she started whispering. I also learned some very basic ASL and used that for things like "thank you". For a long time nobody knew whether she was physically mute or just emotionally traumatised (she would shrug when asked), until the first time she yelled to warn someone of incoming danger during a fight. Nowadays she speaks at low volume with people she trusts and just doesn't talk around the rest of everyone. Vocal affectations help me get into character, and not talking for long periods (specifically not shooting off sassy quips) is a challenge I was interested in taking on, so the two combined into my tiny quiet Elf.