The image from this tweet seems to offer the missing fifth clue for the coded message from Deus Ex: Human Revolution, as it contains the following: "c m / n 7 / p g / g w / + j / # s / 2 a / 8 z / 0 !" (thanks ^Drag0n^). That leave us with:

Original message from the game:

    okM8-+Ds4Dui?lMh$Mzvm14SBqe7;G.l6=u74b?mkh-45Ki60d+98XBpCku7

Also from the game:

    5 - / ! f / f q / x c / q y / d 3 / ? x / t $ / j #

Via this tweet:

    a d / u k / w 0

Via this tweet:

    r 5 / i e / y p

Via this tweet:

    7 2 / m 1 / . 4

Via this tweet:

    c m / n 7 / p g / g w / + j / # s / 2 a / 8 z / 0 !

Update: This all apparently leads to this page, where clicking on the illuminati pyramid offers a login prompt (thanks Panickd) and this audio file (thanks Lazeroth), which sounds like Morse Code. Meanwhile, the Eidos Montreal Community Website offers this: "We got a lot of cosplaying fans asking where they can get Adam's coat. Here's a little something to help you along... o . / l l / e ; / 6 u / ; 6 / h + / v ? / k r / 1 i" (thanks ^Drag0n^).