>>283228148
Who again? I'm just stating how the story goes, I don't see what is repetitive about that. Araragi specifically comments on Shinobu being just the same (and if I remember correctly says about the same about himself). The entire arc is propelled by his paranoia. It is pretty obvious and one is missing a lot if that goes over their head. He is freaking out about last names in the typical way he does about things. He starts by fearing that it'd be wrong for him to erase Hitagi's last name (even planning a trip to a place that shares the name). He then also becomes afraid that Shinobu's name seal is weakening. So he comes up with the idea of adopting her to give her a much stronger name. This has the added bonus of helping her blend in. The adoption also ties into another key point in the story, him wanting to get Hitagi and Shinobu used to each other. He shows obvious paranoia about it potentially going wrong. In the scene where he discusses his future with Hitagi finally, it reaches comedic levels. He has to go as far as to talk to Hanekawa in his head over it. But Hitagi takes it all very fine despite his antics. There are other miscellaneous gags like this throughout too in typically Monogatari fashion. At one point he fears that he shouldn't have a gun despite it being part of his job. Another, he fears Hitagi is going to berate him for being a pervert. In general, he still acts pretty Araragilike.
tldr: Araragi is as Araragi does.