Constant infighting of the core devs, useless communication on the mailing list, not a single worthwhile feature being implemented in 15 years, even if perl6 and Larry designed tons of them suitable for perl5, total destruction of the syntax and the core. The better counterexample was perl6 with stricter processes and some capable devs remaining, but still it's another minefield.
Now, the Perl Pumpking (a sort of Benevolent Punching Bag for the Next Release; they do have the ability to decide which patches go in, but usually don't wield it like a dictator) along with the dev community, does their thing...the pumpkin gets passed along every year or three, and things continue. And, Perl 5 is developing nicely in a way that it didn't for about a decade while there was so much uncertainty. The Pumpking existed before Larry left Perl 5, but acted more in a support role (as I understand it), so it seems like it took a while for it to become an acknowledged executive position when Larry faded from view in Perl 5 development.
I think Guido is doing the best thing for Python. If his heart isn't in it, stepping back in a clear way is much more helpful that drifting away and leaving a void of leadership with no one feeling empowered to step up. There are people who are recognized as being contenders for the throne, and there's already a long-standing community process. I think Python will be fine.
A wiki leads to more structured argumentation, can be re-ordered and edited and doesn't get out of control. Sometimes I also use github issues, because I can update the issues there. But on big issues a wiki page is better.
Such a mailinglist discussion is mostly drama without much content.