So does perl & PM attract people with an interest in linguistics, or perhaps foster an interest in language?

No. Neither PM, nor CB is representative. People without communication skills, or with little interest in them, aren't attracted to PM, and certainly not to the CB. People who don't speak English well enough won't come to PM either.

The fact that non-native speakers of English post here in English doesn't mean that Perl attracts people with a linguistic interest. It reflects several things:

• People not being able to post in English don't post on PM.
• English is a required subject on high schools around the world.
• English is a the de facto common language in the IT world.

Now, if PM saw postings in other languages than English, and those would get as many replies as postings in English, then you might be able to conclude something.