What is a good style for documenting OS X hotkeys on web with markdown?
I'm not sure it's set in stone anywhere, but the convention for Ask Different seems to be along the lines of

&lt;kbd&gt; Cmd ⌘ &lt;/kbd&gt; &lt;kbd&gt; Ctrl ⌃ &lt;/kbd&gt;  &lt;kbd&gt; Opt ⌥ &lt;/kbd&gt; &lt;kbd&gt; Shift ⇧ &lt;/kbd&gt; &lt;kbd&gt; T &lt;/kbd&gt;
 Cmd ⌘   Ctrl ⌃    Opt ⌥   Shift ⇧   T  

giving the abbreviated name &amp; key symbol, no + between

It's not as tidy as the Apple way, admittedly.

I'm not certain for 'key equivalents' but maybe
 Opt ⌥   Shift ⇧   \  = »
as your option 2.

BTW, I use System Prefs > Keyboard > Text to generate these quickly in Stack Exchange
(which apparently only works in Safari, not Firefox or Chrome, see Replace text with predefined value in browser)