According to J Peterson 10% of the workers in an organization do 90% of the work. And when an organization starts going downhill, those 10% leave. Eventually those who are left don't want to do any work, and the work they do is usually not good enough. But since they essentially own the organization now they have their egos at stake and they want to take credit for it. I wouldn't be surprised if SMF went this way.
Probably, although I think the Original Dude who started it is still there, but everyone is arguing with him and vice versa.
Also interesting to note (if I remember correctly) is that XenForo was started by vBulletin developers. Basically, vB was awesome due to 2 primary developers. vB was then bought out or something, they left and started XenForo, and vB went to pot.
You can tell these guys are pretty good because the code is insanely well organized (which also means, unfortunately, that without documentation, it's nearly impossible to even write an add-on).
I had to write my own add-on to make old media embeds from the old forum work in this one... I literally had to put bits and pieces of code examples from their support forum together and just play with it until I made it work. I still don't quite understand how I managed it.
But like I said, that should change in time. It just means that for now, customizations of this forum are pretty much not gonna happen.
About posts per page: it's set to 15 like the old forum default. It's not customizable per user, mostly due to "pretty URLs".
As for post excerpts on listing pages, that's set to the default of 140 characters. The max is 240, which actually looks worse and doesn't give you much more info anyway.
For the most part, all of these things are stuff I already compared to the old forum in an attempt to make it as close as possible to The Old Way. But a lot of it is just restricted and/or done differently.