Re: man page command or convention for subheaders?

I originally asked:

A FreeBSD man page I'm trying to edit uses ".Sh" for the
main headers.  Is there a macro or formatting convention
for subheaders kind of like HTML's <h1> <h2> <h3>, or
like text documents have Chapter 1, 1.1, 1.2, 2, ...?

Christian Weisgerber <naddy@mips.inka.de> kindly replied:

Check what's documented in mdoc(7).

Got it.  Thanks!
Under "Physical enclosures" are macros for surrounding text in
double quotes, single quotes, parentheses, etc.
I can understand using .Dq to get typographical quotes, but is
there an advantage to doing, say, .Qq foo rather than just
having "foo" outright as text, or using .Aq text rather than
just writing <text>?
 -WBE