> In communities where many individuals share a common sign language, deafness doesn't function as a disability in the same way it does when few individuals speak sign language.

Isn't that somewhat obvious? If you only speak Greek, it's a disability if you're not in Greece, but an advantage if you're there.

I think it's a pity that sign language is almost never taught outside of for hearing impaired kids. Every person could have great use of sign language being commonly spoken. It lets you communicate silently and at long distances.