Post History
I agree with others here that if you've been told not to make changes in style, it's likely that the writer's interpretation was that you should leave things like this alone. But you're the proof ...
Answer
#3: Attribution notice added
Source: https://writers.stackexchange.com/a/48391 License name: CC BY-SA 4.0 License URL: https://creativecommons.org/licenses/by-sa/4.0/
#2: Initial revision
I agree with others here that if you've been told not to make changes in style, it's likely that the writer's interpretation was that you should leave things like this alone. But you're the proof reader in this case, so I wanted to give you an "out" in case you hated the sight of it. If "The style of the novel is very traditional and the use of punctuation is conventional throughout", you could argue that leaving it there would change (or challenge) the style of the rest of the novel. That's more lawyering than writing, though, and there's plenty of evidence that writers of fiction can use - and have used - punctuation like this.