Quote Originally Posted by chaika
The thing is that people address you (formally) using your name and patronymic, but you don't introduce (or sign) yourself with these two names, you use all three or only firstname or two initials and lastname. You don't call yourself by name and patronymic any more than you would call yourself in English by firstname-middle name
That's a good point.

name and patronymic is as formal as signing yourself
initial plus lastname,
D.Chaika
In Russian using initial plus last name is really a formal way to sign a letter, while nobody ever would sign a formal letter with first and patronymic names only (without the last name).