Broken formatting when using HTML5 <section> element

[exz]

When using <section> HTML5 element, the resulting markup is invalid because some paragraphs isn't closed properly.

Reproduced with WP 3.3, TwentyEleven theme and no plugins.

Example markup attached to this ticket. Paste into html view of the WYSIWYG editor and publish. Resulting markup also attached.

[exz]

markup to reproduce the bug

[exz]

resulting output

[solarissmoke]

19543.diff​ illustrates where the issue is.

However, the same applies to pretty much all the other block-level elements which can contain flow content - e.g., header, footer, nav etc - where an unclosed paragraph at the end needs to be closed. It's not clear to me why currently only div, form and address get this treatment? The original changeset r4565 doesn't say much either.

[MikeHansenMe]

Here is a list of elements that may need addressed, some are not supported yet.
<article>
<aside>
<command>
<details>
<summary>
<figure>
<figcaption>
<footer>
<header>
<hgroup>
<meter>
<nav>
<ruby>
<rt>
<rp>
<section>
<time>
<video>
<source>
<track>
<canvas>
<datalist>

[MikeHansenMe]

See ticket #21173, this will likely fix this problem.

[MikeHansenMe]

The problem does not seem to be resolved with the fix of #21173 as I thought it may. Problem still exists exactly as described.

[sabreuse]

This is no longer happening. I assume it was fixed by the TinyMCE HTML5 overhaul in [23153]