In response to a comment here https://en.wikiquote.org/wiki/User_talk:Kalki#April_3
I was told <poem></poem> can't currently be embedded in a list item.

So I did a little test :

#Item1
#item2
#Item3 <poem>
Line 1 
Line 2
Line 2</poem>
#item 4

Generates:

<ol><li>Item1</li>
<li>item2</li>
<li>Item3 <div class="poem"></li></ol>
<p>Line 1 <br />
Line 2<br />
Line 2
</p>
</div>
<ol><li>item 4</li></ol>

Which is clearly not what was intended.

When put in manually:

<ol><li>Item1</li>
<li>item2</li>
<li>Item3 <div class="poem">
<p>Line 1 <br/>
Line 2<br/>
Line 3
</p>
</div>
</li><li>item 4</li></ol>

The desired result of a 4 item list with an embeded poem is correctly inserted, but having to specify manual <br /> renders the class "poem" less useful.

This to me, appears to be a further example of the parser or an extension apparently making the WRONG decision about where to close or "tidy" certain tags, ( see some of my recent Bug reports, for other examples.)