Prevent WordPress from wrapping tags with P and BRs

While building a new theme I found that WordPress wraps all <samp></samp> tags with <p></p>. According to specs, <samp> represents (sample) output from a program or computing system. It’s not a block-level element, it can be used inline, as well as <kbd>, <var> or <code>.

The problem is WordPress wraps this tag with paragraph. I managed to solve this issue with this code:

function righter_filter_ptags($content) {
    $content = preg_replace('/<p>\s*(<a>)?\s*(<img .* \/>)\s*(<\/a>)?\s*<\/p>/iU', '\1\2\3', $content);
    $content = preg_replace('/<p>\s*(<iframe .*>*.<\/iframe>)\s*<\/p>/iU', '\1', $content);
    $content = preg_replace('/<p>\s*(<samp .*>*.<\/samp>)\s*<\/p>/iU', '\1', $content);
    return $content;
}
add_filter('the_content', 'righter_filter_ptags');
</a>

It actually strips Ps from images and iframes as well. While it gives the expected results – all <img>, <iframe> and <samp> tags now have no wrapping paragraphs, WordPress now adds <br> tag before <samp>. I’m working in ‘Text’ mode and writing everything in one line, with no line breaks. Here’s the sample code:

We have not only <code>code</code> tag, but also <kbd>kbd</kbd> and <samp>samp</samp> tags.

and here’s sample output in html source code on the website:

<p>
    We have not only
    <code>code</code>
    tag, but also
    <kbd>kbd</kbd>
    and
    <br>
    <samp>samp</samp>
    tags.
</p>

It looks exactly this, with all line-breaks. Everything is fine except this <br> tag right before <samp>. Any ideas how to remove it? Did a lot of googling, no result.