Wayne Harris to Anton Shepelev:

> I see your use of commas match my intuition about them,
> but I, so far, have not found an English grammar, or any
> book, that would clearly spell out these rules to me.

I have never consulted grammar books about punctutation, but
I recommend to you the following books from my definitive
list of manuals of English Grammar:

  1.  The Grammar of English Grammars,
      by Goold Brown

  2.  Manual of English Grammar and Composition,
      by John Nesfield

> If I may, let me ask some questions.  My intuition says I
> should always isolate a vocative in between commas.  ``Hi,
> Anton.''  However, I pretty much never see anyone writing
> that way.  Isn't that a grammar rule?

Of course, your intuition is both logical and grammarical.
Nesfield, for example, says under rule 214 (c) for the
placement of the comma:

  After the Nominative of an address--
    Friends, Romans, countrymen, lend me your ears.

> You wrote ``furthermore, [...]''.  That also matches my
> intuition.  But I often see people ignoring this comma.

I put that comma because I should pause there were I
speaking.

> Perhaps this is an optional comma.  Is it?  What is the
> book you go to to cite such rules?

I don't think it optional but Nesfield disagrees:

  After an adverbial phrase at the commencement of a
  sentence (Here, however, the use of the comma is
  optional):
    In fact, his poetry is no better than prose.

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