WordPress MU

Is there a way, codewise, to use the include-syntax for framing content in an article?

Not sure exactly what you're asking here. Can you give an example?

I am also looking into how to add a link into a post. Is it standard html or []

:|
You can add links in posts with standard "a" html tags...
Adding supplemental text automatically to posts can be done by editing the wordpress core files.

<a href - Is this what you mean by "a" html tags?

I don't want to assume, just want to confirm...

Yep.