Coming back to Silent Storm. Finding clues is often about doing certain missions in certain order under certain conditions in order to gain access to secret missions and better understanding of the story. Not as deep as overworld strategic mode, but still a very nice addition, especially considering that the rules of what you have to do are not arbitrary and gamey, but logical and derrived from story.
My point is, regardless, for completionists, it comes down to doing ! missions before ? missions. That way, we yield all clues and get to explore all sectors for +experience points and +itemization.
I wish modders would mod this game properly and fix its issues properly (they never did)... so much could be done to expand its questing, reactivity and tactics etc.
But this is such a niche game...