I had been using the "-- " to separate signature in my emails. Now it looks like this:
-- Best regards, Nikolay. http://blokhin.us
As it turned out, it is fully compliant with Internet standards track protocol for the Internet community rfc2646:
4.3. Usenet Signature Convention
There is a convention in Usenet news of using "-- " as the separator line between the body and the signature of a message. When generating a Format=Flowed message containing a Usenet-style separator before the signature, the separator line is sent as-is. This is a special case; an (optionally quoted) line consisting of DASH DASH SP is not considered flowed.