That would be JR Conlin, national treasure. Worked with him on YDN in 2007 and Netflix in 2009; veterans of the Netflix API team will never forget his hack day entry, which was "Mac and Me" playing on a toaster oven.

What is he notable for in the context of Mozilla?

Maybe read the blog post? Crazy suggestion, I know.

Skimmed it before asking. It's written for people who already know who the author is. Hence the question.

Staying out of the public eye for his entire tenure. I remain envious.