Please remember that at the Metro Wiki we use British English spelling rather than American English (so if you see "favourite" instead of "favorite", "organise" in place of "organize", etc. then please do not change it). This is for the simple reason that the Metro series started out in Europe, thus it makes sense that European (British) English spelling rules are used here and we respect that. Those who repeatedly go around changing the spelling on the Wiki articles to American variants will be treated as trolls and blocked.
Of course, this applies only to articles - not to discussions, blog posts, talk pages, user walls, and so on. In conversations, you are more than welcome to use whatever spellings are normally used where you live or whatever way you were taught. Also, in cases such as the "Armory" level of the first game we retain the original spelling and do not change it to "Armoury", as that is how it was written in the game (as is usually the case in the games industry, products normally receive only an American English version).