title_body: How to auto-left justify text in personal kindle documents
upvoted_answer: HTML has to be clean for conversions. Often webpages may use custom/extra styles which confuse Kindle or these plugins.  
  
  One idea would be to paste the contents onto a MS Word file and then send the MS Word file to Kindle. 
  
  Paste the text of article to MS Word from a web browser. (Make sure to choose to paste TEXT ONLY). Apply only two styles: HEADING1 to the headline and NORMAL to the body. Don't manually style anything. 
  
  If you want, you could right-click the NORMAL style button and make sure justified is checked. But I'm not sure it will work (or it is even necessary). 
  
  At that point, you can send to kindle. Because Kindle is receiving a clean/unformatted document, it should convert it fairly well. 
  
  I actually think that sending a MS Word doc to Kindle is a lot easier than some of these browser-based plugins. Of course, you may end up losing lists, centering, colors, etc.