If Coscott is right about the Vow protecting "the world" and not "its people", then it very much did change Harry's >terminal values.

OK, I misspoke. It did not change what Harry feels are good terminal values. He may not in any way choose to assist (even by being passive) someone who would want to change that terminal value, but as long as he has not realized what Coscott may have realized, then letting people with terminal value "make sure human life goes on" know about this Vow will not be in conflict with his Vow. They can then come to their own realization. Basically Harry is unfriendly, but he's not intelligent enough yet that he can predict the outcome of every action like, say, Celestia does. He can still accidentally out himself and be dealt with.

The intended meaning of the three persons making the vow have to match, or the Vow won't work. And I think >that two randomly chosen Death Eaters, who have absolutely no idea that people could survive without the >Earth, who don't even suspect that there's been manned spaceflight, would indeed think that "the world" is "the >Earth".

But the last part (when to ignore the Vow) depend only on Harry and Hermione's subjective evaluation. So what the Death Eaters think is not really in question.