Excellent, extensive article. Thank you.
I have some worries though. Where are my coins at a safer place? Leaving on Poloniex in my account or leaving them on Poloniex but being lent out?
In case of a hack is it safer to have them in another user's account (lending)?
About the coming Segwit: I think it would be safe withdrawing everything from Poloniex for those difficult times.
In the event of an exchange hack, I don't think one option would really be safer than the other. I agree, withdrawing from the exchange in advance of August 1 is my preferred option. But on the other hand, if you do that you'll have to navigate any potential fork yourself in regards to upgrading wallet versions, syncing to the right chain, etc. Big exchanges such as Poloniex will have a plan in place for that, and I'm sure many people will simply find it easier to just let them deal with it.