Why this code showing error in W3C validator "character data is not allowed here"

<blockquote>all visible objects, man, are but as pasteboard masks. 
        But in each event -- in the living act, the undoubted 
        deed -- there, some unknown but still reasoning thing 
        puts forth the mouldings of its feature from behind 
        the unreasoning mask. If man will strike, strike 
        through the mask. All visible objects, man, are but as pasteboard masks. 
        But in each event -- in the living act, the undoubted 
        deed -- there, some unknown but still reasoning thing 
        puts forth the mouldings of its feature from behind 
        the unreasoning mask. If man will strike, strike 
        through the mask.</blockquote>

It does not giving any error in this validator http://www.onlinewebcheck.com/

and not in https://addons.mozilla.org/en-US/firefox/addon/249/