"A fellow jaded script reader" sent me an email last week, asking me to "Please do a blog about the obnoxious overuse of exclamation points, underlining, bold, or italics in DP. How many times have you seen: "That's right, Steve has a twin!" Just because a writer uses an exclamation point, it doesn't make their lame plot twist surprising. Uggghhhh."
For the most part, I agree with "Jaded," though he's really talking about two annoying things - exclamation points and asides to the reader. This happens to be one of those times where I'm reluctant to make a blanket statement against them. I agree, it's annoying as all heck most of the time. The real problem is that the writers who use these kinds of asides use them a lot.
And yet, I can see instances where this sort of aside might be helpful, particularly when the implications it underlines are going to be more clear when performed than when written. In other words, if "Steve has a twin!" is a reveal that comes out visually (say through a character looking at pictures, or a scene that shows Steve with his twin without having them speak or confirm their relationship), without dialogue that explains it to the audience, it might not be a bad idea to include that note. Every now and then I read a script where those clues are essential to understanding the twist. Of course, those scripts are also often so badly written - and overwritten - that a reader needs that explanation to make sense of it.
"Jaded" does have a point, though, and if you're finding that your readers require a note like this to understand your plot twists, it might be worth going back and making sure that you've set up these twists properly. Then, if you do include such a note, be conservative with the italics, exclamations and underlining. Use no more than one of those at a time. Also, since these kinds of notes are often seen as a crutch, limit them. My gut feeling is that three of these are the most that should be in any script. Don't leave your audience feeling you have such little regard for their intelligence that they need every twist spoon-fed to them.