Can I place a comma after a conjunction beginning the sentence?

Question

Is it correct practice to place a comma after a conjunction (that begins the sentence it's in)?

• So, Nathan draws the curtains to see what's beyond his dungeon.

• But, I don't see the point in trying so hard!

I have often seen commas being used in such instances. But, a quick google search seems to imply it's wrong.

1. One of the most frequent errors in comma usage is the placement of a comma after a coordinating conjunction. We cannot say that the comma will always come before the conjunction and never after, but it would be a rare event, indeed, that we need to follow a coordinating conjunction with a comma. When speaking, we do sometimes pause after the little conjunction, but there is seldom a good reason to put a comma there.
   — Rules for Comma Usage, Grammar.ccc.commnet.edu

2. Two specific situations call for the use of a comma before "and." The first is created when we have three or more items in a series. [...] The second situation occurs when "and" is being used to coordinate two independent clauses. [...] The use of the comma would also apply when any of the seven coordinating conjunctions (and, but, or, nor, for, so, yet) join two independent clauses.
   — When to Use a Comma before "And", Getitwriteonline.com

The sources of both the excerpts seem reliable enough. This puts me in doubt.

Many people erroneously believe that beginning a sentence with any coordinating conjunction (especially, and and but) is wrong in the first place. I suppose that's why this construction was not considered in the texts above.

The more I think about this, the more I'm convinced that this is probably a grammar myth.

Answer 1

A comma after a coordinating conjunction (and, or, but) is only acceptable when the comma is the first of a pair of commas bracketing a ‘supplement’—a phrase or clause which lies outside the main structure of the sentence and interrupts the flow of thought.

  And, as if that were not enough, he went on to sneer at the victim.
     ^---------------------------^  

  But, as you said, there is no point in trying too hard.
     ^------------^

In other circumstances the comma is effectively ‘disjunctive’ and subverts the joining effect of the conjunction.

This counterproductive comma is becoming very common in contemporary business writing; I suspect it represents a hypercorrection by people who have misunderstood the need for commas bracketing supplements, or think it lends formal ‘elegance’ to their writing.

Answer 2

Your sources are correct, at least for standard American English (I can't say for sure about other dialects). Very rarely, if ever, should a comma come after a coordinating conjunction; this is the same no matter where in the sentence the conjunction is. Your second example should correctly be "But I don't see the point in trying so hard!" without a comma. (I could imagine an author adding a comma after but for dramatic effect, to indicate an unusually long pause; but for that purpose, a dash would be standard.)

This also doesn't change if the conjunction is followed by a word or phrase that should be followed by a comma. The word or phrase is still followed by a comma, but there is no comma after the conjunction:

• "As far as I can see, there's no point in trying so hard."
• "But as far as I can see, there's no point in trying so hard."

But:

None of the above applies to your first example sentence. Sometimes in that sentence is an adverb, not a conjunction. When a sentence starts with an adverb that modifies the main verb, standard American English almost always allows (and in some cases requires) a comma after the adverb. (I'm not aware of any times when standard American English wouldn't allow the comma, but there may be some obscure cases.) That example sentence would be correct either with or without the comma, but with the comma is more typical:

• "Sometimes, Nathan draws the curtains..."
• "Sometimes Nathan draws the curtains..."