thank you for this interesting plugin. I've been playing with it a little. I've noticed that the style.css wasn't loading on front end editing. So i dived into the source code.
In /wp-content/plugins/wordpress-wiki-plugin/wiki.php, function output_css on line 1342, i think you should have :
echo '<link rel="stylesheet" href="' . plugins_url('wordpress-wiki-plugin/css/style.css') . '" type="text/css" />';
instead of :
echo '<link rel="stylesheet" href="' . plugins_url('wiki/css/style.css') . '" type="text/css" />';
because the plugin folder is not named 'wiki' but 'wordpress-wiki-plugin'.