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 [sutta](http://www.sacred-texts.com/bud/bits/bits077.htm) doesn't say that the Buddha allowed him to commit suicide. When Mara reported this to the Buddha, venerable Godhika committed suicide. Then the Buddha saw what has happened and said that he has attained Nibbana. 

According to Bhikkhu Vinaya, the only allowable act that comes close to committing suicide is rejecting medication, if you are suffering from a terminal illness and being a burden to everyone around you.