comments.js

/*
 * In that case, I don't insert comment in my text. Instead, they are shown on bottom and they have an anchor that
 * links to the paragraph on which they were created.
 */

  var paragraphsSelector = $('p');
  var commentselector = $('.comment');
  var comment = new Array();
  var commentdomints = $('.commentdom');

// iteration on each comment coming from commentselector
for (var i = 0; i < commentselector.length; i++) {

    // define paragraph for comment : get the index number for the paragraph stored in database. 
    // It's the same as domPath (see below)
    comment['dom'] = commentdomints.eq(i).text();

    // get paragraph id associated to comment
    // This is where the problem happens.
    comment['paragraphid'] = paragraphsSelector.eq(comment['dom']).attr('id');
    
    // set anchor for return button to paragraph
    commentselector.eq(i).find('.return-to-paragraph').attr('href', '#' + comment['paragraphid']);
  };

  /*
   * Show comment-adding button when hoovering a paragraph
   */

  $('article p, article blockquote, article aside').mouseover(function(e) {
    paragraph = $(this);
    offsetcom = paragraph.offset();
    domPath = $(this).index();
    $("#new-comment-button").show();
    $("#new-comment-button").offset({ top: offsetcom.top, left: (offsetcom.left + em(55)) });
    
});
  /*
   * Add the comment input textarea when clicking on button
   * The index of the paragraph is put in a hidden filed to be sent to server with comment content
   */

  $('#new-comment-button').click(function(e) {
    $('.nav-panel-add-comment').show();
    $(".nav-panel-add-comment").offset({ top: offsetcom.top, left: offsetcom.left + em(57)});
    $("#comment_content").focus();
    $(".nav-panel-add-comment #comment_dom").val(domPath);
});

Quand ça marche si tu veux je peux refaire une passe sur ton JS pour l'opti un peu :)