Supposedly a famous internet figure, from Finland. He is known for extreme use of sarcasm, flaming, but also at times for witty conversations and helpfulness.
While the author wasn't able to find more than a few logs, it seems that the person has gained a large level of (in)famy in all things web, being refered to the greatest flamer ever, et cetera. Also, perhaps as a joke and the background of his nick, it's said that he gets his "temperament" from, ever-so-typical of the finns, drinking large amounts of coffee.
Some state that he used to be an owner of a large IRC Network, a game site and a forum, that quite simply snapped. Also, perhaps one of the original developers of IRC.
Coffee-Addict also refers to someone who stays on nearly 24/7, presumedly because of large use of coffee.
<nebulian> Stop trying to be a coffee-addict, dude.
<TunaFM> and here our next contestant for the title of Coffee-Addict, Leprechaun!
(Lemur) You've been awake for how long? Coffeeaddict or something maybe?