Our service does use family-linking in our @font-face rules for browser-compatibility purposes. A side effect is that if you select a bold font and use it with an element that has a font-weight of bold (H1, for example, has a bold weight by default) or select an italic font and use it with an element that has a font-style of italic (e.g. EM), the browser will take the bold or italic font and then transform it mathematically to match the element’s font-weight/font-style. The resolution is to ensure that all elements using our web fonts have a font-weight and font-style of ‘normal’.