He's still the buck-stops-here person for the module owner system in the Mozilla Project. He's not involved with the Mozilla Corporation as far as I can tell.
Maybe that's just obvious if you're familiar with the governance structure of the Mozilla Project but not clear to people who haven't been involved in it...
In any case I've seen one technical issue escalated to Brendan so far since he resigned, after mailing list wrangling back and forth for a while got nowhere. He made a call on it (a compromise of sorts, as it happens), and people abided by that call from what I can tell.
He clearly has a lot less impact on decisionmaking now than he did before, which is what you see in his comments. I can totally understand why he feels the way he does. But I think he's underselling the importance he still has.