Of course, one can convert a segwit coin back to a bitcoin by spending it to yourself in a non-segwit transaction.
Not necessarily true. If anyone can spend the SegWit transaction, then miners can in theory orphan your second spend if there are long enough range chain reorganizations. Given the SegWit booty that will start accumulating when SegWit goes live (~Aug 23), then long range change reorganizations are economically plausible.
Drat! You're right! Even worse!
(Shelby - if you're reading this - I have no plans of creating a steemit account, which is the reason I reply here)