Font Awesome accessibility issue. Use <em> tags instead of <i>

As a general guideline, you should use em for emphasis instead of i for italic text because italic text is normally used only to imply emphasis.

In this case, you are using i for icon, which is nonsense (and confusing your accessibility checking tool). Use a span instead. That doesn't come loaded with any inappropriate semantics.

On a strict and semantic HTML, font icons have to be tagged with spans:

<link href="https://maxcdn.bootstrapcdn.com/font-awesome/4.6.3/css/font-awesome.min.css" rel="stylesheet" />
<span class="fa fa-camera-retro"></span>

Font Awesome examples appears with <i> (italic tags) because of abbreviation coding. Just it.