Before HTML5, ISO-8859-1 was the default character set for HTML 4. That encoding was a superset of ASCII, and didn’t have typographic quotes. That meant that it was mandatory to encode curly quotes.
The default encoding in HTML5 is UTF8, which does (of course) have typographic quotes.
We tried to bridge the gap in Tinderbox 6 by encoding characters that would, if not encoded, cause problems in HTML 4.0.1 Transitional. ^value($Text) will give you utf8, which is fine if you know you’re using HTML5, or if your page adopts the UTF8 charset. This gives you a way to export to either new or old HTML formats.