I asked my friend if he could guess who I romanced in DAI. He guessed Cullen first. I thought that was funny.
Then he guess Solas, and I said that's right. Then he said "He's boring."
I agreed with him so I wouldn't give anything away, but I realize now that him making himself out to be boring IS THE TRICK.
(SPOILERS FOR DRAGON AGE INQUISITION START HERE)
If you think someone's boring, you're not gonna ask them questions. You're not gonna try learning more about them, cause you know why? Because they're boring. And that's how he got away with it.
Leliana noticed the vagueness of his answers but by the time she found out, it was too late. Plus, Solas does trick you in his own way. Remember when he reveals to you that the orb Corypheus wields is elven? You can investigate, which prompts the Inquisitor to ask this:
"All right. What is it and how do you know about it?"
Solas then goes on to elaborate about what it is, using many uncommon words and introducing some concepts that may be new to you. But in doing so, he avoids answering the question of "how do you know about it".
Well played, trickster... well played.