Here's a sentence from no less than Edward Gibbon (The History of the Decline and Fall of the Roman Empire):
Twenty-two acknowledged concubines, and a library of 62,000 volumes attested the variety of his inclinations, and from the productions which he left behind him, it appears that the former as well as the latter were designed for use rather than ostentation.
Why is there a comma after concubines? I see this construction fairly often, where the second part of a compound noun is set off in commas.
Also, shouldn't Gibbon have put a comma before the "from the..." as in "....and [,] from the productions which he left behind him,"?
Here's another example, from the first paragraph of the work, where I've put a note in brackets after each questioned use:
In the second century of the Christian Æra, the empire of Rome comprehended the fairest part of the earth, [Editor: comma use here?] and the most civilized portion of mankind.... The image of a free constitution was preserved with decent reverence: the Roman senate appeared to possess the sovereign authority, [Editor: comma use here?] and devolved on the emperors all the executive powers of government. It is the design of this, [Editor: comma usage?] and of the two succeeding chapters, to describe the prosperous condition of their empire.