How does core.extensions.php really work?

We ran into an interesting issue with LG_tinymce extension recently. In debugging I was able to figure out that if I echo out the return value from the extension itself, then the correct javascript script tags get written into the Dom. If I do not echo it out myself inside the extension however, then after it gets returned it fails completely.

I guess I’m just not sure where extension return values go, or how they are processed so now I’m stuck as to how to further trace this problem.

Thanks. -J