"""INT. OFFICE -- DAY -- JOHN

does things. Picks a coffee mug, takes a sip."""

Ed Neumeier (<3) does that on his scripts. I like how the double-dash makes things stand out.
Can it we used on Spec?

What's the story for adding things at the end of Slug Lines? Is it a shooting script thing or a stylistic choice?
I like how they work because they make things harder (at least for non-natives like myself), thus fewer chances to go verbose (again for non-natives like myself ), and because they "hook" you to read what happens next.

Quoted from Ares """INT. OFFICE -- DAY -- JOHN does things. Picks a coffee mug, takes a sip.""" Ed Neumeier (<3) does that on his scripts. I like how the double-dash makes things stand out. Can it we used on Spec? What's the story for adding things at the end of Slug Lines? Is it a shooting script thing or a stylistic choice? I like how they work because they make things harder (at least for non-natives like myself), thus fewer chances to go verbose (again for non-natives like myself ), and because they "hook" you to read what happens next.

I don't like this at all. Wouldn't use it - IMO anyway

I have to admit though that the lines above were an example written by me to emphasize the concept.

I understand the concept and it's fine if in an office environment where there is more than one character. Say five characters are all sitting at desks... then the location would always be the Office, but an extra note at the end of the slug works.

However, it is still unnecessary. You don't need your slugs to stand out. All you need to do is write well.

INT. OFFICE - DAY
that's all you should do.
If there's another office featured, it would be INT. JOHN'S OFFICE - DAY