You may want to place two lines together in your
presentation but, please don’t underline text!
Underlining text is considered in much the same way as
swearing, or cussing as my US friends would say - its
crude. Good design looks interesting, its never messy.
With the infinite array of design possibilities in
powerpoint there are far better ways of creating emphasis
to a piece of text. The use of colour, font selection,
text size, placement.
I hope this gives you some ideas.
Gary