Vertical bar and comma in hash function input
I don't know anything about IEEE 802.11i, so I can't be sure about my answer, but hopefully this provides some insight.

From the way in which the formula is written, $H$ is probably some sort of keyed hash algorithm—probably HMAC.  HMAC takes two parameters: the secret key to the MAC and the data to hash.  The first parameter is probably the secret key to HMAC, with the concatenated data being the data to hash with HMAC.