alt Hacker News> "Intimate communication" here almost certainly refers to shared memory.
No, shared memory is addressed later within the same answer.
> Using shared memory to communicate with complex data structures is pretty much equivalent to dynamic linking.
The first part of the answer clearly includes programs sending each other "complex data structures", including nested JSON data, over pipes.
And the first part of your quote starts with
> If the main program uses fork and exec to invoke plug-ins
Which limits a lot the relationship between the original program and the "plug-in" concept. I mean, we literally have binary proprietary blobs used as kernel drivers...