So, I got curious and dug around to see if there was more support for the Owl guide. I found this in the Oxford English Grammar and it supports Owl and where the punctuation falls (always inside the quote).
"One writer, signing his letter as "Red-blooded, balanced male," remarked on the "frequency of women fainting in peals," and suggested that they "settle back in their traditional role of making tea at meetings."
It also says "for the citation of single words, italics are often used in print, normally represented by underlining in handwriting or typing."
The community of editors at CMoS supports the use of italics for single word interjections instead of quotes.
For the original example, either quotes (punctuation inside) or italicizing would be considered grammatically correct according to Oxford, CMoS, and Owl.
Regardless of the style you choose, as long as it's consistent you'll be fine. I lean to the CMoS, so I'd probably go with the quotes, but my gut says that italics would work better at not interrupting the flow of reading.