Fridge Brilliance: Oliver mentions that he "did his homework on both of you" before letting Felicity and Diggle into Team Arrow, which would explain the Contrived Coincidence of Oliver recruiting one of the world's best hackers and a man with useful A.R.G.U.S. connections. Another explanation is that the Blatant Lies he told Felicity and his Ditch the Bodyguards stunts with Diggle were a Secret Test of Character.
When Ivo tells Oliver his time to choose is over, he points the gun at Sara first. This was likely a conscious choice because he knew Oliver couldn't resist protecting whichever girl's life was under immediate threat. Knowing that Oliver would save Shado under the same circumstances, he lets Sara live so that if his plan goes awry and he loses the mirakuru, which he did, he would still have a chance to get her back on his side and get what he wants. Unfortunately, as we later see, she didn't trust him enough to go back.
Ho Yay: When Barry mentions to Felicity he can understand if she wants to date Oliver, Felicity comments, "Sounds like you want to date him." Barry does not deny it and even blushes.
