Discussion Groups / English Usage / October 2006

It's not incorrect, but it would be equally correct with the first
comma omitted, and I wouldn't be surprised if some people defended the
omission of both commas.

English punctuation is nowhere near as settled as people think it is.

Very often, at least with punctuation, "correct" does not mean "not in
overt error" but "truly presenting the intended thought"; thus, whether
that sentence is "correctly" punctuated depends on what it is supposed
to convey.

As it stands, the comma pair sets off the phrase "anyway" as a
parenthetical comment--almost the equivalent of writing " John is full
of sh.t (anyway) so why even respond?"

While that does meet the first test for parenthetical material--can the
material be dropped without rendering the sentence ungrammatical or
meaningless?--it leaves one wondering whyever that "anyway" is being
isolated.

Thay "anyway" is plainly a so-called "sentence adverb" modifying the
clause "John is full of sh.t": think of the sentence as reduced to
"John is full of sh.t[,] anyway."  We would want a comma only if there
is some reason to set off the adverb as wanting quite a special
emphasis, as "He acted, promptly" would be distinguished from the much
more common "He acted promptly."

Setting off "anyway" in that manner in the subject sentence seems
neither sensible nor idiomatic, even if not "incorrect" in a technical
sense.  A casting that seems much more likely to represent the intended
thought would be:

"John is full of sh.t anyway, so why even respond?"