My boyfriend insists that commas and other forms of punctuation should be outside parantheses. I insist that this is (of course) completely and egregiously incorrect in American usage.
We told her the truth, but she didn’t pay attention (of course.)
vs.
We told her the truth, but she didn’t pay attention (of course).
(That’s British usage).
(This is American usage.)
Please help to settle this once and for all.
Thanks!