Time travel, the past "still existing" - and utilitariainism? I don't buy any of that either - but in the context of artificial intelligence, I do agree that building discounting functions into the agent's ultimate values looks like bad news.

Discounting functions arise because agents don't know about the future - and can't predict or control it very well. However, the extent to which they can't predict or control it is a function of the circumstances and their own capabilities. If you wire temporal discounting into the ultimate preferences of super-Deep Blue - then it can't ever self-improve to push its prediction horizon further out as it gets more computing power! You are unnecessarily building limitations into it. Better to have no temporal discounting wired in - and let the machine itself figure out to what extent it can predict and control the future - and so figure out the relative value of the present.