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Thanks in advance for your help. Maybe it's the lack of sleep, but I'm over thinking commas in compound sentences where the second clause has an implied subject.

Which is correct?

a) The doctor finished the shot, and removed the restraining wires.
or
b) The doctor finished the shot and removed the restraining wires.

c) The shapes refused to come together, and became lost in a numbing darkness
or
d) The shapes refused to come together and became lost in a numbing darkness

And what if we change the coordinating conjunction?

e) She could taste blood in her mouth, but could not feel the right side of her face.
or
f) She could taste blood in her mouth but could not feel the right side of her face.
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Of a&b, b is correct. The two actions take place within moments of each other and have the same subject.

Gramatically, d and f are correct as well. But if you were reading c&d out loud, you'd pause, I think, and so therefore a comma is acceptable.

Likewise with e&f - if you are giving strictly a factual recitation of her condition, then do not use the comma. But if you want to create a little more drama with an implied pause, then use it.

Commas are half art and half syntax. I say this as a writer. Don't let people who are focused strictly on rules tell you otherwise. If the comma helps clarify or convey a mood, then use it, even if the rules say it's not necessary.
Comments  
Unfortunately, I posted this topic without realizing that I was not logged in. Since anonymous posts have to be moderator approved, I have two threads going on this question. See also:

http://www.EnglishForward.com/English/CommasCompoundSentencesSecondClause-ImpliedSubject/cvwmv/Po...

The passage in question is part of a disjointed narrative from a character passing in and out of consciousness. AP style would remove the commas that separate the bold phrases, but I'm torn. The commas, in this case, seem to convey a specific pacing. They also speak to the character's addled state of mind.

Drawing the corner of her lip inward, she could taste salty blood in her mouth, but could not feel the right side of her face. Shapes took on a distant, twisted vagueness. She was lying on the ground, that much was certain, but the shapes refused to come together, and became lost in a numbing darkness.