code consistency

[Hannie Dumoleyn]

In unity-introduction.page I see the word The Dash in 3 different ways:
The <gui>Dash</gui>
The <em>Dash</em>
the Dash
Does it look better if only one formatting code is used. One may argue 
that it depends on the context. Since I am doing this proofreading for 
the first time, I want to know what the policy of the docs-team is. Am I 
too picky, or should we be more consistent?
Hannie