Well Palo Alto is about as far away from San Francisco as Arlington is from Dallas, so technically you could consider the '85 SB to be the one case where a team played in their home city.
Good point
Wikipedia says: “No team has played the Super Bowl in their home stadium. The closest have been the San Francisco 49ers who played Super Bowl XIX in Stanford Stadium rather than Candlestick Park, and the Los Angeles Rams who played Super Bowl XIV in the Rose Bowl rather than the Los Angeles Memorial Coliseum.”
Further down:
“There Has Never Been... a team which played in a Super Bowl in their home stadium.”
However METRO AREA is not the same thing, true.