He did write "The fact that there's no market for startup ideas suggests there's no demand. Which means, in the narrow sense of the word, that startup ideas are worthless."

What I mean when I say playing with words is that he qualified that statement with "in the narrow sense of the word." He was also referring to startup ideas in particular.

This discussion is getting to be a little ridiculous because you're splitting hairs and and missing the point entirely.

No, you are missing the point.

So, now it is qualified by startup ideas? Then where did all the "ideas are worthless" phrases come from? (like this thread).

If you agree that in general, ideas have worth - some more than others - then we are on the same side. :)

Perhaps from other people who contracted a phrase because they understood what the context was? How'll you know unless you read the original source?