[Tim]
But I'm not sure it's fully appreciated just how active Guido has been in those at times. The "accepted/rejected" at the end of major PEPs is just a small part of that. Along the way, e.g., it's been pretty common to see a "Save your breath. That's not going to happen." from Guido to end a distracting alternative (sub)proposal persistently promoted by one (or a few) very active and/or loquacious posters.
[Antoine]
I think that only happens on python-ideas. We've long had a problem with that mailing-list (but at least it allows to avoid such discussions on python-dev).
I'm unclear on whether you view that as opposing or confirming my point ;-) I view it as confirming: yes, the BDFL has played this role mostly on python-ideas, where the dirty work of developing general PEPs is intended to take place, while they're still at best half-baked. If someone only follows python-dev, they're unaware of most of these BDFL pronouncements.
The latter may think "oh, big deal - a PEP is posted to python-dev, and then Guido has weeks to make up his mind about whether to accept or reject it". They're only seeing the end of a sometimes very messy process. Most things on python-ideas never make it to python-dev at all.
PEP 572 was (IMO, and Guido's, and a whole bunch of others) posted to python-dev prematurely, so anyone who doesn't follow python-ideas should know that the firestorm on python-dev was just a hint of what python-ideas can be like routinely ;-)