The difference between X is true vs. I believe X is true is irrelevant. > I would probably have titled it "I think FTL travel might not be impossible". Again,

The difference between X is true vs. I believe X is true is irrelevant. > I would probably have titled it "I think FTL travel might not be impossible". Again, what does “not impossible” mean? The only meaning, logically, is “not impossible = possible.” The fact that you’ve used the word “not” implies a two state system. LEM applies. The original title made sense. Your proposed change to the title is either: equivalent to the original title or logically inconsistent.