I couldn't seem to find this anywhere, so I apologize in advance if this was already posted. Regarding Shatterstar's trait,

Can the placed character have already been given a non-free action prior to Shatterstar using the trait, or can this only be done if the placed character hadn't already been given an action?

I'm gonna say the "can't be given" part should have this qualifier before it "After that character has been placed" but I could be wrong.

You can do whatever you want with the figure until you place it. Well whatever you can do legally anyways. Once its been placed though, it can only be given free actions.

"That character can’t be given a non-free action this turn. "
That's the part of this power's description, I believe, that is genrating the question. It could be expanded upon by stating "That character can’t be given a non-free action from this point on during this turn., which may not be necessary,be stated better, and be considered too wordy(which is something I know I have read that GD wishes to avoid), but would nip any question of intent in the bud.

If the power meant the way that you think that it might be interpreted, it would have wording saying that it couldn't have wording specifically saying so. In one of the only instances where I can think of any type of wording that is somewhat similar as to what you are implying, it would be theme team probs.

In this case it doesn't say anything like that. It was also never discussed with that being the intent at the time the watch list results were announced.

Oh, I know. I think its fine. I'm not questioning it. But to be clear, it could have said "After this character has been placed" and "this turn" could have been left out.

Definitely agreed. But interpreting the wording, meaning and intent is half the fun of the game though, right? hahaha

You were doing one of those Jim Gaffigan things while you typed that out right? You know, whispering really loudly "No, it's not".