15) Separate signatures correctly, and don't use excessive ones

Posting software SHOULD separate any signature appended to outgoing
articles from the main text with a line containing only `-- ' ("dash
dash space"). To quote son-of-rfc1036:

        <<If  a  poster or posting agent does append a signature to an
          article, the signature SHOULD be preceded with  a  delimiter
          line  containing  (only)  two hyphens (ASCII 45) followed by
          one blank (ASCII  32).   Posting  agents  SHOULD  limit  the
          length  of  signatures,  since  verbose  excess bordering on
          abuse is common if no restraint is imposed;  4  lines  is  a
          common limit.>>

Hence, posting software MUST prevent the user from using excessively
long signatures, or at least warn the user against it.  A widely
accepted standard is the so-called McQuary limit: up to 4 lines, each up
to a maximum of 80 characters.

Rationale: Being confronted with (possibly excessively long) signatures
repetitively is, or can be, annoying to many.  Being able to separate
the main text and the signature clearly is important, not only to
prevent the possible mistake of misinterpreting a signature, but also to
enable automatic signature suppression for those who wish to do so.