Edited to remove irrelevant stuff
I posted about quitting the HTML WG on Twitter, but there's only so much one can shove into 140 characters. Of course, I realize that most people will probably be uninterested in a longer writing on my reasons, but that's the advantage of syndication feeds—you can see at a glance whether you want to read beyond the first few sentences of a writing. Or not.
First of all a clarification: I joined the HTML WG once. I quit the HTML WG once. I joined the HTML WG reluctantly, because as I wrote at the time, I'm really not a joiner. I feel I'm best writing in my own space, not participating in a back and forth in email lists; definitely not through quick non-thinking blurbs in an IRC channel, or teleconferences where key players never participate.
I did join, though, and became actively involved. However, I never could figure out the "rules" of the effort, and I found it both discouraging and exhausting. So much so that it drained the energy I needed for the writing I need to do for a living. More importantly, I felt I really wasn't making a difference, and I'm not sure I was willing to play the game in order to make a difference.
A further point of clarification: My decision to quit did not come about because of any exchange I had yesterday with any person. It was a number of factors that led to my quitting, a primary one being the one I just mentioned, needing to focus on work. I'd already decided to quit before yesterday, but was waiting for a specific thread on RDFa to play out. I will mention, though, that some of the reasons why I'm leaving were echoed in that thread, including the hostility of the WhatWG backchannel IRC, and the lack of respect some members of this group have for members of the HTML WG and other W3C groups.
Some of the the WhatWG members seem to think that I've quit the HTML WG more than once, but they are mistaken. I unsubscribed from the WhatWG email lists, because I found the environment hostile. I stopped working on my assessment of metadata use cases, because the HTML5 author, Ian Hickson, suddenly released a new microdata section, changing everything I wanted to write.
I have unsubscribed from the WhatWG mailing list, and that won't change. I have quit the HTML WG, and I may, but it's unlikely, rejoin at some later time. But I have not stopped writing about the HTML5 specification. Whether I make a difference or not, my way of "participating", in the HTML5 effort, and any other, is by writing in this space. And I will continue to do so, in my own time, and in my own way.