Mixing incremental divs and markdown in RMarkdown slides

I work with RMarkdown a bit for slide presentations. One element I noticed is that to implement "appears" in slides using slidy ir ioslides, one had to wrap the relevant sections in div or span tags with class = "incremental". This works like a charm, except when additional text formatting is included, like ** bold ** or * italic * formatting. These text elements are optional after the text. So for example

<div class="incremental">Hello **world**!</div>

      

        
        
        
      

    

would result in this: if every slide hit me with the forward arrow

Slide 1: Blank

Slide 2: Hello!

Slide 3 Hello world !

Thoughts of a direct solution? Presentation option is amazing at the same time!