The 'selection' is what fails routinely for me, but it's been a problem for most versions of windows and depends heavily on what markup is used to display the text.  In word, for example, you can see the selection jump from one clump of text to the next and if you took a look at the openxml that makes that text show up, you'll notice that each clump is in a separate run.

I suspect a similar process is happening in the UI for win8, but I just assumed that it was the touch interface being uncooperative.

I don't like touch very much.