I don't see much of a difference: underline/underscore/emphasize

all 3 would work here.

a rather cheeky assumption: Dude is AE user?

in BE I'd expect to use underline, not underscore, though this might be a personal choice.
Cambridge online has both, but underline is the preferred (the definition is under underline, not underscore - at underscore one is linked to underline)

I would like to add that underline and underscore are two different typographic things that can both be used to emphasize words. Underline is a line under the text that is to be emphasized. Underscore is a short line on the base that might be set in front and at the end of the _emphasized_ word.

yes, I am an AE speaker, and in AE, there isn't much difference in this context.

Well, to me, there is this difference:

I can 'underline' text on the typewriter ( in a second go)

On the computer I get a separate 'underscore' ( _ )and I have to rely on a special function in Windows to get any text underlined . . .

yes, Daddy, but in a figurative sense such as this context has, there's no diff. :-)

Look here:
http://www.google.com/search?client=safari&rl...

o.k. - thanks . . . :-)

None of you seem to realize that the word 'underscore' has reference to music as well!! Both underscore and underline can be used in some cases similar to the German 'untermalen' though LEO has not realized that yet...