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:
Posted by Stan Carey 
Sentence first 