Note: After saving, you have to bypass your browser's cache to see the changes. Google Chrome, Firefox, Microsoft Edge and Safari: Hold down the ⇧ Shift key and click the Reload toolbar button. For details and instructions about other browsers, see Wikipedia:Bypass your cache.
if (mw.config.get('wgPageName') == "Special:Watchlist") {

  $('table.mw-changeslist-line-not-watched').find('td:gt(0)').css('opacity', '0.8'); 
  $('table.mw-changeslist-line-not-watched').find('a:first').css('opacity', '0.68').css('font-style','italic').css('font-size','98%'); 
  $('table.mw-changeslist-line-watched').find('a:first').css('opacity', '1').css('font-style','normal').css('font-size','100%');
  $('table.mw-changeslist-line-watched').find('td:gt(0)').css('opacity', '1').css('font-style','normal').css('font-size','100%');

  $('li.mw-changeslist-line-not-watched').css('opacity', '0.8'); 
  $('li.mw-changeslist-line-not-watched').css('opacity', '0.68').css('font-style','italic').css('font-size','98%'); 
  $('li.mw-changeslist-line-watched').css('opacity', '1').css('font-style','normal').css('font-size','100%');
  $('li.mw-changeslist-line-watched').css('opacity', '1').css('font-style','normal').css('font-size','100%');

  $('#mw-watchlist-resetbutton').remove();

}

if (mw.config.get('wgAction') == "history") {
 
  // Green "updated since my last visit" notices are also not conducive to this setup, 
  // since we're now trying to "demote" checked changes rather than highlight unchecked ones.
  
  $('.updatedmarker').remove();
 
}