The Penguin Dictionary of American English Usage and Style : A ...

punctuation 329
guish that group from the Temple members.
If both groups were outsiders, clarity
requires removing those commas. (A
better treatment would be rewriting.
“Although they produced solid evidence
that people who lived outside the city,
both Temple members and others, had
voted. . . .”)
Unnecessary commas can make a portion
of a sentence appear to be unessential
when it is really essential. A noted
book on language says:
Two years earlier the Scottish physician,
Alexander Hamilton, traveling
along the Hudson, found an immense
number of colonels.
The comma after “the Scottish physician”
makes the ensuing name seem just
an elaboration, unessential to the previous
phrase. The implication is that Scotland
had only one physician. Removing
the comma distinguishes the Scottish
physician Alexander Hamilton from all
the other Scottish physicians. (But see
THE, 2A, end.)
A comma generally should not be
placed between a subject and its verb.
Delete the commas in the two press sentences:
. . . The seller’s only obligation without
a written warranty, is to sell you a
car that is capable of providing basic
transportation. . . .
. . . The established way to prove a
statistically significant improved survival
rate in the patients who have
taken the drug, is for a certain number
in the control group to die.
To place a comma immediately after is in
either of those sentences (and thereby
separate the auxiliary verb from the rest
of the verb phrase) would also be a mistake,
yet some make such a mistake. See
Verbosity (artist) for an example.
Nor should a comma follow the subject
of an absolute construction. “Mangoes,
being cheap, I bought a bunch of
them.” Delete the first comma. See Modifiers,
1D.
Normally two items in a series of two
in a simple sentence need not be separated
by a comma. (See Series errors, 8,
for the rules in longer series.) Delete the
commas in these two samples, from
news stories:
Police said the dead were four construction
workers, and the driver of
the school van.
Hungarians were denied jobs, and arrested
in inordinate numbers.
Those commas are just unnecessary,
slightly impeding communication. Occasionally
such a use can mislead. A memo
says, “Joe: Tell Fred to draw up the contract,
and see me in my office.” If Fred is
the one to visit the office, the comma is
unwanted; it seems to herald an independent
clause, in which “see me” is an order
to Joe. A more complicated version
of that problem comes from a magazine
article, which advises parents:
. . . Insist that your child never give
out personal information—home address,
phone number, school name—
on-line without first asking your
permission, and never agree to meet
someone in person without a parent
being present.
At first, the comma may seem to divide
the sentence into two independent
clauses, in which you, the parent, are
told to (1) “insist that . . .” and (2)
“never agree to. . . .” Actually, “never
agree” is not an imperative but a present
subjunctive; it is subordinate to “insist
that your child,” just as “never give out”
is. Readers can figure out the meaning,
but the comma is momentarily misleading.
(For emphasis and clarity, the main