1. I hated green beans when I was a little boy. (no comma)
2. I hated green beans, when I was a little boy. (a comma)
3. Ann was fond of Tim though he often annoyed her. (no comma)
4. Ann was fond of Tim, though he often annoyed her. (a comma)
Which of the above sentences is not acceptable to native
speakers?
Good question — this is really about comma usage with adverbial clauses.
Let's look at each:
I hated green beans when I was a little boy. – Perfectly natural. No comma
needed.
I hated green beans, when I was a little boy. – Not acceptable. Native
speakers don’t insert a comma here, because when I was a little boy is a
restrictive adverbial clause (essential information).
The comma wrongly suggests it's parenthetical.
Ann was fond of Tim though he often annoyed her. – Perfectly fine.
Ann was fond of Tim, though he often annoyed her. – Also fine. Here the comma is optional, because though he often annoyed her
can be treated as an afterthought or aside.
So the only one that is not acceptable to native speakers is #2.
https://reurl.cc/mYRLoj