After the note about HTML element limitations, I wanted to experiment:

|left align|center align|right align|none/ default align|
|[markdown link][1]|HTML Image:<br><img src="" width="100" title="juicy orange">|<pre>pre tag</pre>|triple backticks just yield ```code spans```
`backtick inline code, with no added breaks`|<code>html code tag</code>|<pre>pre tag with<br>line<br>break tags</pre>|<pre>pre tag with<br>line<br>break tags</pre>
 <s>`> markdown quote`</s><br>This breaks in real posts, but not the preview | >! spoiler |<blockquote>html `<blockquote>`</blockquote>|<blockquote>html blockquote with<br>line<br>breaks</blockquote>
<code>html code tag<br>with inline<br>break tags</code>|* markdown ul|1. markdown ol|<s>html `<strike>`</s>|
Description List (`<dl>`):<br><br><dl><dt>item (`<dt>`) 1</dt><dd>item 1 description (`<dd>`)</dd><dt>description list item 2</dt><dd>item 2 desc</dd></dl>|Ordered List (`<ol>`):<br><br><ol><li>list item 1</li><li>list item 2</li><li>list item 3</li></ol>|Unordered List (`<ul>`):<br><br><ul><li>list item 1</li><li>list item 2</li><li>list item 3</li></ul>|Default aligned list:<br><br><ol><li>list item 1</li><li>list item 2</li><li>list item 3</li></ol>|
|*markdown italic*|**markdown bold**|***markdown bold italic***|# markdown header
<i>html italic</i>|<b>html bold</b>|<i><b>html bold italic</b></i>|<h1>html `<h1>` header</h1>
<sup>superscript `<sup>`</sup>|<sub>subscript`<sub>`</sub>|markdown horizontal --- rule|html horizontal<hr>rule `<hr>`

<sub>([SE allowed HTML tags refresher][2])</sub>

It generally seems, on the surface, to play fairly nice right now! 

Is there any reason this support would foreseeably change in the future?  
Or can this be counted upon as a feature?