Admittedly this might just be a problem with the course material I was looking at, but I was reading some letters between two friends (emphasis mine), Анна and Иван, because apparently Иван was sightseeing in the Urals and Анна was stuck back in Nizhny Novgorod.
Anyway, they sign their letters to each others as "твой Иван" and "твоя Анна", after telling each other "скучаю".
Would this level of familiarity/intimacy be considered "proper" or "normal" for two platonic friends in Russian, especially for friends of the opposite gender?
To me this seems like too much emotional disclosure. Unless you are discussing anger, disclosing any negative emotion to someone to whom you are not related, particularly when they are of the opposite gender, seems like it could be misconstrued as a request for romantic intimacy.
Additionally, saying to someone unrelated that "I am yours" seems like an offer of an inappropriate amount of commitment and loyalty, unless that person is a romantic partner.
Only if I was really familiar with someone would I write "your friend", but this doesn't translate well into Russian, especially for a friend of the opposite gender, because then "твой друг" or "твоя подруга" means "your boy/girlfriend", which would really be the wrong message to send.
In other words, translating the letters literally into English, one has the impression that these two friends have boundary issues. Or am I just misinterpreting Russian culture here?