There's a "we see" or something like it (I'm too lazy to look up the script) in the beginning of Big Fish (and I don't think anyone would fault the writer for that phrase--or anything else in that wonderful story).

In most cases, spec writers aren't targeting an audience of rule-keepers or format grammarians, but studio readers who want to be entertained by a story. The example that you cite from Prisoners presents a story, not a format. There's a bit of formatting there (all caps for what might be considered sound cues: SLAPS and SMASHES LOUD, but the use of all caps also signals the importance of these actions.

I don't think it's possible to be certain what will work for / against the involvement of a hypothetical reader (e.g. bold sluglines), because no one knows the preferences of hypothetical readers, nor is it possible to know the preferences of a real reader unless you know what that reader has specified as a preference. The best strategy in my uninformed opinion is to adopt a rational strategy and stick to it as much as possible. But in general, any strategy that says to the reader "You are reading a script" is not as strong as as a strategy that conceals the artifice of the story. Techniques that emphasize the writer's voice might seem like artifice, but I believe that when they are used effectively, they persuade the readers that they are in the hands of a skilled storyteller and can relax and enjoy what follows.