When combining lists with quotes (or spoilers), something strange happens. The following Markdown:
1. > This is the first quote. 2. > This is the second quote. produces
1.
This is the first quote.
This is the second quote.
so it seems that server-side, the first list item isn't recognized. The previewer doesn't have this problem, as you can also verify by editing this post:
Another example, trying to make quotes part of the list:
1. > This is the first quote. 2. > This is the second quote. -
This is the first quote.
-
This is the second quote.
The preview and end result are the same, but I'm not sure it's semantically correct.
It does seem to work when you add additional content to the list items:
1. A quote follows: > This is the first quote. 2. A quote follows: > This is the second quote. A quote follows:
This is the first quote.
A quote follows:
This is the second quote.

<ol></ol>, with the second being<ol start="2">, each with a blank<li></li>, in addition to two<blockquote>elements, with neither<blockquote>within either<ol>.