[Lichurec]

1) "!important" is not a solution, especially that "css_editor" alone includes declarations with !important which therefore you can not overwrite. In order be able to custom-style the templates one has to be sure that his "customised CSS" WILL be loaded as the very last.

2) in this case JS does not add additional classes. I managed to track down the issue and - from my perspective - it's an error which I can not bypass in any reasonable way.
The contententry template includes <script type="text/javascript"></script> block at the very end. Apparently - rendering this template (which happens if one tries to "edit" someone's post) renders blocks full of <link rel="stylesheet">in place of the script block.

This forces the browser to try to re-download those CSS templates (which it should not do, hence they're already in the browser cache) AND re-render whole page keeping in mind new order of css files ("new" files / files linked lower in the code list will become "more important" and override style declarations from any files loaded / linked earlier).

What's interesting - it's sufficient to have an empty <script type="text/javascript"></script> block in mentioned template for this behaviour to occur… :/

Rendered code looks like:

<!--[if IE]>
<link rel="stylesheet" type="text/css" href="http://test.local/css.php?styleid=4&amp;td=ltr&amp;sheet=css_b_content_entry.css,css_b_toolbar.css,css_b_content_entry_panel.css,css_b_editor.css,css_b_smilie.css&amp;ts=1383582879 " />
<link rel="stylesheet" type="text/css" href="http://test.local/css.php?styleid=4&amp;td=ltr&amp;sheet=css_b_file_chooser.css,css_b_attach_item.css,css_b_link_input.css,css_b_link_content.css,css_b_table.css&amp;ts=1383582879 " />
<link rel="stylesheet" type="text/css" href="http://test.local/css.php?styleid=4&amp;td=ltr&amp;sheet=css_b_poll_fieldset.css,css_b_datepicker.css&amp;ts=1383582879 " />
<link rel="stylesheet" type="text/css" href="http://test.local/css.php?styleid=4&amp;td=ltr&amp;sheet=css_imgareaselect-animated.css,css_jquery-ui-1_8_14_custom.css,css_jquery_qtip_min.css,css_jquery_selectBox.css,css_global.css&amp;ts=1383582879 " />
<link rel="stylesheet" type="text/css" href="http://test.local/css.php?styleid=4&amp;td=ltr&amp;sheet=css_b_link.css,css_b_layout.css,css_b_button.css,css_b_button_group.css,css_b_dropdown.css&amp;ts=1383582879 " />
<link rel="stylesheet" type="text/css" href="http://test.local/css.php?styleid=4&amp;td=ltr&amp;sheet=css_b_icon.css,css_b_tabbed_pane.css,css_b_form_control.css,css_b_form_input.css,css_b_form_select.css&amp;ts=1383582879 " />
<link rel="stylesheet" type="text/css" href="http://test.local/css.php?styleid=4&amp;td=ltr&amp;sheet=css_b_form_textarea.css,css_b_media.css,css_b_divider.css,css_b_avatar.css,css_b_ajax_loading_indicator.css&amp;ts=1383582879 " />
<link rel="stylesheet" type="text/css" href="http://test.local/css.php?styleid=4&amp;td=ltr&amp;sheet=css_b_topicpreview.css,css_responsive.css&amp;ts=1383582879 " />
<![endif]-->
<!--[if !IE]><!-->
<link rel="stylesheet" type="text/css" href="http://test.local/css.php?styleid=4&amp;td=ltr&amp;sheet=css_b_content_entry.css,css_b_toolbar.css,css_b_content_entry_panel.css,css_b_editor.css,css_b_smilie.css,css_b_file_chooser.css,css_b_attach_item.css,css_b_link_input.css,css_b_link_content.css,css_b_table.css,css_b_poll_fieldset.css,css_b_datepicker.css&amp;ts=1383582879 ">
<link rel="stylesheet" type="text/css" href="http://test.local/css.php?styleid=4&amp;td=ltr&amp;sheet=css_imgareaselect-animated.css,css_jquery-ui-1_8_14_custom.css,css_jquery_qtip_min.css,css_jquery_selectBox.css,css_global.css,css_b_link.css,css_b_layout.css,css_b_button.css,css_b_button_group.css,css_b_dropdown.css,css_b_icon.css,css_b_tabbed_pane.css,css_b_form_control.css,css_b_form_input.css,css_b_form_select.css,css_b_form_textarea.css,css_b_media.css,css_b_divider.css,css_b_avatar.css,css_b_ajax_loading_indicator.css,css_b_topicpreview.css,css_responsive.css&amp;ts=1383582879 ">
<!--<![endif]-->