Double htmlPurifying in system/Text/Parser.php, why?

[TSP]

In: 

	public function parse( $value )
	{		
		/* CKEditor sometimes includes these for markers. HTMLPurifier will remove the style attribute so we need to strip them first */
		$value = str_replace( '<span style="display: none;">&nbsp;</span>', '', $value );
				
		/* Clean HTML */
		if ( $value and $this->htmlPurifier )
		{
			$value = $this->htmlPurifier->purify( $value );
		}

		/* BBCode, Profanity, etc. */
		if ( $value )
		{
			$value = $this->_parseContent( $value );
		}
						
		/* Clean HTML */
		if ( $value and $this->htmlPurifier )
		{
			$value = $this->htmlPurifier->purify( $value );
		}

What's the reasoning by running it twice through the purifier? Wouldn't it be enough to just do it once? Either before or after _parseContent. 

I'm also wondering how "safe" you would consider it to be to comment out the second purifyer step to speed up the post conversion task running after an upgrade from 3.4. 

[newbie LAC]

 

[All Astronauts]

^ Hey - I know that quoted guy