ahmad posted:I also believed that was the case (although I didn't know the rule as clearly as you know it, and made it clear here), but it was only after I came across a similar expression that made me turn to the GE. In a Youtube documentary entitled In Search of History: Scotland Yard's Greatest Investigations, I saw that expression.
Punctuation is largely just a matter of convention, and conventions change over time. Historically, it was both common and acceptable to separate subject and predicate with a comma. Thus, the Second Amendment of the U.S. Constitution originally read: "A well-regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed."
Nowadays that punctuation is incorrect, and the sentence is instead written: "A well-regulated militia being necessary to the security of a free state, the right of the people to keep and bear arms shall not be infringed." I agree with Gustavo that there should not be a comma before the appositive clause in your example. It does not adhere to modern punctuation conventions, though I can't speak for Scotland.
Now, Ahmad, I have a question for you. I would like to learn how to add a picture to the body of a post, as you have done above. Could you please tell us what function you selected to do that. You say that it is a screenshot, so I'm assuming you uploaded it directly from your computer. I'd like to know why your photo attachment manifests in the post, whereas Ruifeng's just stayed at the bottom: