Quote:
f you've found sources that support a period rather than a question mark, why look further? You've found what you need.
Because it is interesting, no?
I use this construct (rhetorical tag questions) from time to time and use a period naturally. I never thought about it until I was challenged.
I was surprised that it was so hard to find a rule, or any examples, in my first attempt to look for them.
I think it is a useful construct.
I am still interested to hear what your friend has to say on the topic.