This is the first time I'm hearing the term 'smart quotes' or 'soft quotes'. I googled to see what it is and all I got was some 'smart' quotes. There's an obscure Wiktionary page on smart quotes which also does not really explain what it is. The GitHub page being linked itself is so vague and cryptic it's hard to understand what is even talked about.
To all those who are confused, smart quotes or soft quotes are those context aware quote marks that some word processors insert which depending on context, will put either closing or opening quote marks.