There was in fact a talk given by Greg Kroah-Hartman, one Linux's lead maintainers, about development for the Linux kernel which he titled "I Don't Want Your Code".
He's at Linaro, specfically taking their developers to task for sending bad patches. And they indeed sound horrible, but he's good natured about it.
I'm just starting to accept patches for my project, and honestly I'm flabberghasted that people will send patches that not only don't run, but don't build. And Greg was saying the same thing.
I guess I got spoiled at my last job, where people generally sent high quality patches / code reviews. Although toward the end, I noticed some sloppiness. It wasn't the main reason I left the company, but it started to feel like the downfall... I don't want to work with people who don't know how to submit code reviews / patches.
Indeed, I've seen the same thing. I have considered automatically rejecting any patch made with the GitHub online editor (obvious because the committer name is always GitHub). They are pretty much invariably of shit quality.
This _might_ show a long-term risk for Linux.
Linus has said this a few times -- in general they don't actively try to onboard new contributors.