jQuery(‘.comment .comment-entry’).each(function(){
var words = jQuery(this).innerHTML.split(' ').length;

if(words >= 20){ var text = jQuery(this).html();
var temp = text.substr(0,20);

// Get the visible part of the string
var newtext = temp + '<span class="hide">' + text.substr(20,text.length) + '</span>';

// Recompose the string with the span tag wrapped around the hidden part of it jQuery(this).html(newtext);
}
});