The problem is that punctuation is rarely taught properly in schools, mainly because teachers don’t know the rules themselves!
One of our proofreading and editing course students asked us the other day how to punctuation this sentence:
The grim news came from the chairman , councillor Fred Egerton , aged sixty , who analysed the festival’s successes.
She rightly observed that there are so many rules, she didn’t know which one to apply.
We encourage our students to use the Blue Book of Grammar (BBG).
So with this sentence, if you put commas on either side of a phrase, it can show either a) that the information is extra, and that if it was deleted, it would not change the meaning of the sentence OR BBG commas rules 5 and 6; or b) that the information interrupts the flow of the sentence and the commas make it easier to read the sentence clearly. This is covered in BBG commas rule 7b.
The phrase ‘councillor Fred Egerton’ is not that important to the meaning of the sentence, because there is only one chairman, so that is why there are commas either side (rule 6) and they can stay.
The phrase ‘aged sixty’ is extra information, and could be left out and not change the meaning (rule 5) so the commas can stay.
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