So we had a discussion over on FB about "so" -- again!
As you all know, I want us to punctuate according to the grammar that is going on in the sentence. I believe with my heart and soul that punctuation is an outgrowth of grammar most of the time.
The word "and" and the word "so" simply do not function the same in the language. "And" is a conjunction through and through. It does absolutely nothing else in the language except connect equal elements. When it connects two sentences, it has to have a comma in front of it.
...I walked over to the edge and looked down at the car.
...I walked over to the edge, and I looked down at the car.
So far, so good; right?
The word "so" is, by nature, an adverb.
...He was so very tired that night.
...She is so happy to have the job.
Sometimes we pull the word "so" out to the front of a sentence. When we do, it is STILL AN ADVERB, but it takes on the role of connecting the sentence it is part of to the sentence in front of it. Thus we call it a "conjunctive adverb." It is just like "thus" and "still" and "then."
...He had left the company; so he could not participate in this.
...We went through San Diego; so we did not stop to see her.
It starts a new sentence. When you put a comma in front of it, you create a run-on -- the same as you would if it were not there and you were to use a comma.
...We sent it on Friday; so it should arrive no later than Monday.
...We sent it on Friday. It should arrive no later than Monday.
A comma in either of these sentences creates a run-on sentence.
The semicolon could always be a period; it can never be a comma. And the length of the sentence has nothing whatsoever to do with being able to put a comma instead of a semicolon or a period.
And the rule is that, if the conjunctive adverb is just one syllable, it does not take a comma after it.
I hope you will consider this and really take the time to analyze it from a grammar standpoint. Grammar and the way the words are functioning preclude the use of the comma.
Happy punctuating!
Margie