April mama lurking...
I had no idea that this: "the area around your belly button will sink in a bit rather than poke out" was an indication of being posterior! That was my first pregnant belly to a T. I was a bit self-conscious about it, really-- and all my belly pics have my hands up so you don't see it.

Nobody told me that my dd was posterior, but I've always sort-of wondered, just based on my labor pattern (which wasn't back labor, but long and intense). Hmmm... more to think about.
Um, ok, now I feel like a real doofus. I just googled "posterior pregnancy" to get a better image of fetal positioning (which is always mushy in my head), and it said posterior meant the baby would be born face up. Duh. Mine was (MW's comment-- as I was pushing on my back-- was "it has a pretty face-- it must be a girl"). How have I managed to be this ignorant about this when I try to be so well-informed about birth in general?

Oh well, it's good to know if that was the case. Better late than never...

See, this is why I lurk-- always learning.