I read that every interjection should be separated from the sentence, no matter where it's placed, with a comma. If that's true, would phrases such as these require a comma after "oh"?
"Oh yeah" or "oh, yeah"?
"Oh my God" or "oh, my God"?
I feel as if the phrases "oh yeah" and "oh my god" are both treated as interjections and that they shouldn't need a comma after the "oh." Am I wrong, or is there a rule to this?