Signatures

This post is going to be a bit short, but I have a question for you all to consider. How do you sign your letters/emails? And what does the way you sign your letters/emails mean? For example, one of my favorite professors always signs his name "tim" on every email I've ever sent him. Is that giving me permission to call him by his first name? Sometimes I sign my emails with just my first initial - usually only to people I'm super close/casual with, like my father. My CWIT mentor signs her emails "plr", which are her initials. When I write to my friend Yna, I like to sign the letters in more flowery ways - "Very truly yours", for example. Not for any particular purpose, just because I write her often enough that I like to add that for a slightly different flavor. According to Dr. Shields, signing my letters that way is a sign of my Western training, the fact that I include language of love in my letters to a friend. You all know now that I have saved several letters over the years, and they usually end with "Write Soon", etc. How do you sign your name? Does it have any significance?