I'm not certain on how they developed, too, but there are a lot of similarities, yeah, especially in British derivatives. NZSL and ASL (as in Australian) are really similar, and British Sign Language is only another step away. American Sign Language is pretty different in that it uses primarily finger-signs, if I'm not mistaken - but I can still get the gist of what people are saying, which is pretty interesting. There are definitely "loud talkers" in sign languages, and often it's not just that their signs are larger and more expressive, but they'll make more noise as they do it.
I wonder if that indicates a difference in origin between American Sign Language and the British derivatives. I guess that just highlights how different sign languages are from spoken languages, at least in terms of development. It's kind of funny to me that a "loud talker" in sign language is noisier in general, but I can see that. Is it also considered to be . . . not "rude" maybe, but mildly inconvenient?
Yeah, I'd be interested in learning about the development of the two. I've never come across anyone thinking of it as rude or inconvenient, it's just part of the culture, I guess?