Wordpress does bad things with shortcodes and p tags

esc-html-no-no.php

<?php
    
    // ...
    
    function eschtml_func( $atts, $content = null ) {
	  return htmlentities( $content );
    }
    
    add_shortcode( 'eschtml', 'eschtml_func' );
?>

esc-html.php

<?php
    
    // ...
    
    function eschtml_func( $atts, $content = null ) {
	  return htmlentities( $content );
    }
    remove_filter( 'the_content', 'wpautop' );
    add_filter(    'the_content', 'wpautop' , 12);
    
    add_shortcode( 'eschtml', 'eschtml_func' );
?>

From a post about the various ways you can stop wordpress wpautop clobbering the content in your enclosing shortcodes and doing surprising things with P tags at Enigmatic Ape Blog : http://www.enigmaticape.com/blog/wordpress-shortcode-p-tags-an-html-escape-plugin/