Bet you weren't expecting that Narihira thirst trap, huh?
It quite funny because this new information basically makes us all perverts, as we have seen several male characters' bare hair plenty of times (at least Narihira's, Michizane's and Tokitsura's). Oh, well... At least we're together in this...
Now, on the topic of Nene's name, this volume was released on October 2015, so that "currently" no longer applies. This year's taiga drama "Toyotomi Kyōdai" goes back to calling her "O-Nene-dono", so it was more of a trend than something that came to stay. But I do remember that they called her "O-Ne-san" in Gō: Himetachi no Sengoku (2011 taiga drama), so I can confirm that we indeed went through a phase of calling her Ne instead of Nene (I'm sure there are other examples, but I can only speak based on what I've watched). So in the end, it all boils down to personal preferences (I think I'll always be team Nene.)
Anyway, with this, volume 4 is finally 100% complete, so on to volume 5 we go!