Question: When asking around, I've never heard anyone agree that a young, healthy person should end their life by suicide. But I also don't know what reason there is for that consensus. 

Did Buddha teach anything regarding what makes life worth living?

Answer: 
Have you been to see a doctor about this? Depression can cause life to lack appeal. Why is life worth living is one of those questions that cannot be answered in words, it's an inner feeling that doesn't need an explanation that most have felt at some point. It's a sign of good health to have a passion for life. 

If whatever is causing you to feel that life is bleak changes, as it inevitably will, a passion for life can automatically emerge in you.

Life and death are two aspects of the same movement. By dying, the Buddhist would say, you don't really escape, for your return to life is guaranteed. Whether it is life as a human or not is another matter. So, what else is left if suicide doesn't improve things?

Given that life and death are one continuous movement, ever occurring, it makes sense to learn to live and learn to die.

Living in misery and dying in misery are common but not necessary.

Get tested for depression, and perhaps meditate with a good teacher in a monastery. The compassionate surroundings may trigger a change towards joie de vivre in you.
The following only is relevant if you follow Buddhism\ the following are all from Shantideva's text: 

1. "Upon finding the boat of human birth now, cross the great river of suffering. O fool, there is no time to sleep, for this boat is hard to catch again."
2. When shall I encounter the extremely rare appearance of the Tathagata, faith, human existence and the ability to practice virtue,
3. Health , daily sustenance, and lack of adversity? life is momentary and deceptive; and the body is as if on loan.
4. With such behavior on my part, a human state is certainly not obtained again. When a human state is not achieved, there is only vice. When a human state is not achieved, there is only vice and how could there be blessing?
5. If I do not perform virtue even when I am capable of it, what then shall I do when fully dazed by the sufferings of miserable states of existence
6. For one who does not perform virtue but accumulates sin, even the expression "favorable state of existence" will be lost for a thousand million eons.
7. Therefore, the Blessed One (Buddha) stated that human existence is extremely hard to obtain, like a turtle's head emerging into the ring of a yoke on a vast ocean.

The text goes on and on. Too lazy to type the rest. I'll leave you with one of my favorite lines:

"Enemies such as craving and hatred are without arms, legs and so on. They are neither courageous nor wise. How is it that they have enslaved me? " 

-If you are a Buddhist and accept certain Buddhist ideas and thoughts then the above may help answer your question.