Bug in <p></p>

[Looimaster]

We all know that WordPress adds unwanted <p> and </p> everywhere which is alone a frustrating bug for me.

But if you do something like this manually:
<p>test <samp>test2</samp> test3</p>

Then it will be displayed like:
<p>test <samp>test2</samp></p><p>test3</p>

But this...:
<p>test <b>test2</b> test3</p>

...will be displayed like:
<p>test <b>test2</b> test3</p>

It performs wrong match of </p> with </samp>.

Duplicate of #18807.