Really, if you're going to get a picture of the guy at least use the one with the pimp coat and the accordion. I've got it on my computer, I'll have to see if I can scrounge up a URL.
Probably wrote most of the stuff you read at TIL.
What's Tedders, chopped netch?
I'm not exactly sure, but I think he worked on the main quest for Morrowind. I believe he worked on KoTN as well, but as far as I know, he was not involved with Oblivion's main quest at all. Chances are that he is working on the main plot for TESV. From what I've seen in a few of his posts, he is unhappy with some of what happened with Oblivion (one of them being the reintroduction of Mithril armor, if I remember correctly)
If I remember correctly MK started off as the lead designer for Morrowind, and wrote much of the backstory. I believe he left before TES III started full production after Redgaurd's release, but his work still formed the foundation of the game. I could be wrong but I also think he did some modeling and artwork for TES III.
As others have pointed out, his writing fleshed out some elements of Oblivion's main quest (including books), in addition to some of the general writing he did for the game.