I do like "a mess o' greens" greens in ramen soup. But I agree with you: for salad, bok choy is much better young or very young.
The trendy, expensive thing is apparently "microgreens", which take the idea of baby leaves to an extreme. Depending on who you read, microgreens are just the seedling leaves (cotyledons), or one pair of real leaves, or at most two pair. That's just one step past seed sprouts!
http://www.johnnyseeds.com/t-m...
I used to over-cook bok choy stems in soup. They would get mushy and be undesirable. Now my policy is to get them barely heated all the way through, so they stay crisp. That's why I cut them into thin strips or pencils, so that a brief simmering is enough to get them hot.
Best of all is to eat the stems raw.
