About the "Taboo" thing Kojima mentioned awhile back, is in MGS V if you have not noticed

[Kresnik]

PullusPardus said:

You should play Portable Ops first, or watch the cutscenes there is a lot of plot in that game.

See, I'd read that Portable Ops isn't canon or something like that.

Still, they're both Vita-compatible in the UK so I'll certainly give it a try.