My guess is a typo, possibly supposed to be 11 or 12? Is 1998 too early for TF2 design to be occurring?
Team Fortress 2 was announced in 1998
According to Wikipedia. So that looks plausible.
The post however talks about gathering feedback from players of TFC, which didn’t come out until 99. Maybe Robin meant the original mod, which he also worked on, or maybe he just misremembered at what point TFC came out or when they actually explored the death stuff that resulted in the freezecam.