Quotation marks for ‘emphasis’ are common in unedited writing but rare in formal prose, where italics are the usual approach. Bold and underlines are occasionally used; ditto *asterisks* and _underscores_. ALL CAPS and Initial Caps are sometimes favoured but can suggest shouting, humour, or a headline effect, so they’re more suited to informal contexts: both are popular on social media, for example.
There’s an anomalous example in a book I just read, Rough Ride: Behind the Wheel with a Pro Cyclist, an engrossing memoir/exposé by Paul Kimmage (Yellow Jersey Press, revised edition, 2007). It occurs about halfway in; Kimmage is describing the effect of Stephen Roche winning the Tour de France:
Back in Ireland, Stephen’s Tour triumph was celebrated as a national victory. He was welcomed home to scenes of incredible adulation in an open-top bus tour of Dublin. Cycling was ‘the’ sport, and winning the Tour made Stephen the greatest sportsman the country had ever produced – and one of the most popular. [underlines added]
When the word the is emphasised, its pronunciation changes: the vowel shifts from an unstressed schwa /ə/ to an /iː/ ‘ee’ sound, like thee. This usage comes under sense 13 in Macmillan Dictionary, sense 9 in Collins, and sense 5 in Oxford.
In the short clause Cycling was ‘the’ sport, the idea is to indicate that cycling was the most important or fashionable sport at the time. The quotation marks (aka inverted commas) around the definite article achieve this – since the is a function word, there’s no risk of ambiguity – but the technique is unexpected.
As a writer I’d have used italics, as a reader I’d have expected them, and as an editor–proofreader I’d have changed or flagged the quotation marks. It’s not a serious error, but in edited prose the usage is non-standard (or at least unorthodox), and is therefore of editorial interest to me. Have you seen it in similar contexts?
I didn’t plan to read Rough Ride during Bike Week, but the timing was apt. On Friday I joined a few dozen others on a bike buffet, which was a terrific event: a delicious meal distributed around the town, each course in a different location and a bike ride between them.
The main course was al fresco by a wildflower meadow on the west side. Galway’s skyline is low enough to offer a sliver of bay between the rooftops and the shower clouds: