Sure, the one I was thinking about is a tendency to strum really really hard, and you would think this would be an easy habit to break, but it is surprisingly difficult.
I don't think of hitting the strings hard as a "bad habit" in and of itself. Being able to play with a broad dynamic range is very useful, but not necessary to have fun and make good music.
I remember seeing a Paul Gilbert instruction video a while back where he talked about the importance of being able to play a single note, while hitting it with a full on rock and roll windmill arms technique. This is mostly a matter of muting the other five strings effectively. But hitting a note like you mean it really matters.
Plenty of people start on acoustic. It doesn't teach bad habits in my opinion. Acoustic teaches the good habit of more precise fingering, because when you fret a chord slightly off it sounds worse on an acoustic vs an electric. At the end of the day it really doesn't matter much which one you learn on. For me acoustic wins because you can pick it up any time and start playing immediately. There's no fiddling with amps and cables, no power cords or batteries to worry about, and I can wander around the house to different rooms while playing if I want.