Seems most of the debate is about what KISS stands for and various versions have been handed down.
The original KISS is "Keep it Simple, Stupid". This phrase was in use during the Apollo Project in the 1960s in US.
In the later years, Bill Clinton's 1992 campaign team twisted it to the related expression "It's the economy, stupid!".
The question is what version the writer of the article meant. If u read the first para - the writer uses the words "Simplicity" and "Stupid". So I think he meant
Basically he is the kind of person who has done a lot of "Mattress Investments" - buy and tuck the shares under your mattress. Keep dusting your mattress once a year for next 20 years and voila you have got a winning stock.
I don't think that he could ever be a great mutual fund manager.