Is it professionally acceptable to place a dash after a question mark in the following example?
Bob: 'I don't like asking Matt but I need some help.'
Peter: 'Why don't you go and ask him to help you? - He's a really nice guy.'
I want to use the dash to highlight the reason for the function of the question which is to encourage Bob to ask.
No, because the dash (which should properly be an M-dash, like this — ) is an interrupter. You can use it at the end of a broken-off phrase, or if a sentence is interrupted, but you need some kind of narration in between.
examples:
"Why don't you go and ask him to help you? He's a really nice guy," Peter added.
"Why don't you go and ask him to help you?" Peter quickly added, "He's a really nice guy."
"Why don't you go and ask him to help you? I know you don't like him —" Peter continued, his tone clearly indicating what he thought of Bob's attitude, "— but he's really a nice guy."
"Why don't you go and ask him to help you? I know you don't like him —" Bob made a face; Peter shrugged. "— but he's really a nice guy."
"I don't like to ask Matt for help — "
"Why don't you go and ask him to help you? He's a really nice guy," Peter added.
I think the key here is that you know what it would feel like to try to speak with these sentences in mind, but you don't know what it would actually sound like.
Most people, in speaking, do not speak in complete sentences. David Mamet is a master of portraying realistic dialogue on page.
But most people, in reading well written, properly grammatical text, don't realize it is not at all how they would speak.
So the answer is to not mix the two. Don't try to write as it would sound and write grammatically at the same time. The disparity between the two is jarring.
