Yeah a peace sign makes zero sense. I don't think that's it. If they were worried about being "down with the kids" the ghost would be wearing shades with a backwards hat on. The "2" is more about it being Ghostbusters 2.0. They are back in business. New and improved. But the *real* reason, is that they just didn't think people would care. It's the "2" because this is a sequel. And it's the dumbest thing in the movie. And I love GB2. But it's stupid. That's the real reason. But the in universe explanation is that this is Ghostbusters 2. That's what they file on their taxes. Ghostbusters 1...ah Jesus never mind. The mental gymnastics I'm doing to explain away the "2" is exhausting.I said this before, but the peace sign was big in 1989. It's a "we're back and down with the kids, honest" gag as much as it is a "two". It's just that time has diluted memories of the former so subsequent generations see it as confusing.
Yeah I've always thought it was kind of weird that they had the 2 on their uniforms in the second film. I know it was probably just for marketing but the business itself is just "Ghostbusters" and not "Ghostbusters 2" so it's just kinda odd they made that choice. I would think it was even more weird if there was a 3 on the uniforms in this movie.
I guess the modern equivalent would be if the new no-ghost logo was flossing while holding up three fingers! (I'm 41, cut me some slack if we're beyond flossing now! )
I use to think it was the peace sign until I realized it doesn't make any sense. They are Ghostbusters. It'd be like if "No Smoking" signs had a picture of the cigarette giving a thumbs up. Sends a weird message.