A Gist that highlights non-standard font-sizes on Wikipedia and outputs all computed font-size values into a console table and log.

fontSizeHighlight.js

const treeWalker = document.createTreeWalker(
  document.body,
  NodeFilter.SHOW_ELEMENT
);

const fontSizeTable = {};

while (treeWalker.nextNode()) {
  const node = treeWalker.currentNode;
  const computedStyles = window.getComputedStyle(node);
  const fontSize = computedStyles.getPropertyValue( 'font-size'); 
  const fontSizeNumber =  parseFloat( fontSize ); 

  if ( fontSizeTable[ fontSize ] ) {
    fontSizeTable[ fontSize ].push ( node );
  } else {
    fontSizeTable[ fontSize ] = [ node ];
  }

  if ( !Number.isInteger( fontSizeNumber ) || fontSizeNumber === 13 || fontSizeNumber < 12 ) {
    node.style.backgroundColor = 'pink';
    node.style.outline = '2px solid red';
  }

  node.classList.add( 'tree-node', 'fs-' + fontSize.replace('.', '_') );
}

console.table( fontSizeTable );
console.log( fontSizeTable );