HTML comments are not removed when using `filter_html`

[bear454]

markdown = Redcarpet::Markdown.new(Redcarpet::Render::HTML.new(filter_html: true))
markdown.render("Hello, World <i>Boo!</i> <!--comment-->")

 => "<p>Hello, World Boo! &lt;!--comment--&gt;</p>\n"

Shouldn't filter_html remove the comment, instead of escaping it?