The title is specifically intended to be a double entendre (and kind of a clever one). If you really want to disassemble this whole thing, it's the clever use of "diet" that makes the pun.
In Rails world, the topic of fat models (lots of impl methods, code, etc) comes up all the time. This isn't trolling. It's called being creative vs. "Use different code to remove more code from your models".
Gimmie a break..
And yes, like another poster said, I doubt DHH uses any thought or loses sleep over how HN will pick up the post and tear it down. He created a great framework, has built up an inspiring company, and wanted to share some thoughts. Doesn't go any further than that in my mind.
>Yes, he is trolling HN with the title, because you can get sadly predictable conversations like this one.