Commas and Conjunctions

Hello, this is my first post here. I am a grammar enthusiast and wonder if there is a consensus about when it is proper to use commas before conjunctions. I recently read that commas should be avoided if two independent clauses are separated by a conjunction (note that the rule doesn't apply to dependent clauses, where commas are necessary). However, I am fond of using commas in some situations that are in opposition to this rule. For example, suppose we have the following sentences:

"I have a jacket but it doesn't keep me warm."
"I have a jacket, but it doesn't keep me warm."

"I have a jacket and it keeps me warm."
"I have a jacket, and it keeps me warm."

The two sentences without commas satisfy this rule but they do not necessarily have better flow. It seems to me that a comma before the but provides the sentence with better flow, regardless of the fact that but separates two independent clauses. However, a comma does not seem appropriate before the and. Has anyone heard of this rule? What are your feelings about it? Does it have merit or is it better to play commas by ear?

Ah, welcome to English Forums, Chunes-- a grammarian after my own heart! I agree that the flow's the thing in many comma considerations. I often present it as a function of clause length and complexity: the longer and more convoluted clauses require commas, where the simpler ones do not. It's a matter of clarity vs clutter, to my mind.

And there is no consensus, fortunately, so we can do as we please. For instance, in contradistinction to what you recently read, Purdue University advises:

"The comma is a valuable, useful punctuation device because it separates the structural elements of sentences into manageable segments. The rules provided here are those found in traditional handbooks; however, in certain rhetorical contexts and for specific purposes, these rules may be broken.

1. Use commas to separate independent clauses when they are joined by any of these seven coordinating conjunctions: and, but, for, or, nor, so, yet."

(But I have never run across different approaches to 'and' and 'but'.)

'Oxford comma', eh? I'll wow 'em with that 'un down at the pub later.

With a bit of luck, you'll be able to eat out on for weeks!

That's not an Oxford comma. An Oxford comma refers specifically to items in a series not when using a conjunction and two subjects.

Chunes wrote:

"To my parents, Ayn Rand and God." Without the comma after Ayn Rand, it would seem that the author's parents are Ayn Rand and God. With the comma, it is apparent that it is merely a list with three entries. Thanks for all your replies.

Even with the comma this still reads to me as if Ayn Rand and God are the author's parents. Imagine if this were continued: To my parents, Ayn Rand and God, who have helped me. There, it reads (at least to me) as if Ayn Rand and God is in apposition to my parents.

If you want the dedicatees in that order better is:  To my parents; Ayn Rand; and God.

Otherwise: To Ayn Rand, God and my parents avoids the specific from being included in the generic.

In longer lists semi-colons are sometimes essential. Compare:

We were accompanied by Mrs Clarke, the vicar's wife, my sister-in-law, May Smith, the butcher's wife, the local teacher, my sister, Elizabeth Jones, Mrs Brown, Lotte Schmitt, the German lady, Mrs Green and Lucy Williams.

We were accompanied by Mrs Clarke, the vicar's wife; my sister-in-law; May Smith; the butcher's wife; the local teacher, my sister, Elizabeth Jones; Mrs Brown; Lotte Schmitt; the German lady, Mrs Green; and Lucy Williams.