Reading through the core and looking at nearly all of the helpers/plugins etc. that are available, I notice there are a lot of comments.
CakePHP is structured in such a way that it is very simple to determine where things are and what they are doing. Is it really necessary to comment all of this code? Does it make the source more messy or is it really useful? When you grok the comments, do you find them useful? Or do you even read them?
UPDATE: Here is a sample of comments taken from the CakePHP Core connection manager for example:
/**
* Loads the DataSource class for the given connection name
*
* @param mixed $connName A string name of the connection, as defined in app/config/database.php,
* or an array containing the filename (without extension) and class name of the object,
* to be found in app/models/datasources/ or cake/libs/model/datasources/.
* @return boolean True on success, null on failure or false if the class is already loaded
* @access public
* @static
*/