What is the function of the comma here? Is it to avoid ambiguity?
He should send his troops across the river, either in sufficient numbers to overwhelm the opposition forces or (in sufficient numbers) to hold the bridge.
I am, by the way, having some difficulty in understanding the purposes of commas, especially in such sentences as this one:
On the other hand, he did work hard.
Is the purpose of the comma here to mark the adjunct "on the other hand" as modifying the entire clause (with the comma functioning as a delimiting comma), or is it to mark it off as parenthetical?
Note: I am unsure whether this question is suitable for this site. However, after posting this question on the English Learners StackExchange and receiving linguistically deficient answers, I have decided to repost it here.