Mr Light wrote:
I'd wager "Winter Soldier" only means something to a few thousand people
If that's true, then the fact that that was Cap's ol' sidekick Bucky from the comics in the first film is significant only to at most a few thousand more.
Most people filling the seats aren't going to care how the sequel hangs together with the first film, how it hangs together with the other Avengers films, or especially how it relates to the comics. They're only going to care how the film hangs together on screen the night they see it, just as they did for the first film.
If they need to piece it together with any other source material to make it work or to make it significant, or if they need
to rewatch the first film first, then the sequel won't do so well, and that will be it for the film series.
In other words, whether the title's a spoiler isn't on the radar for most viewers.