> Is everything what you call "reader directive" actually a reader directive?

No, you're right. The title should be something else. Any suggestions?

We could just title it "#! syntax" or "Hash-bang syntax", but it might
be nice to group other prefixes besides "#!" together in the same table.

> For example, "#!eof" seems to be a datum syntax used by some Scheme,
> not a reader directive.

True. #!eof doesn't change the reader's settings in any way. Neither do
#!optional and the like.