For my two bits worth, I've been on it since '98. The only reason that I can think of is that you could have been 'shearing to a headwind', which would give you an increase in indicated airspeed. If the SAT was decreasing, you could also expect that you could have an increase in indicated airspeed. The aircraft has a tremendous amount of energy and anything that is 'out there' that tries to disturb it, always shows up in the dynamics until the energy state gets sorted out.
As for turbulence penetration speed, the difference from a cruise of 0.834 to get down to 0.82, is so minuscule. By the time one could get the aircraft slowed down, you'd probably be out of the turbulence. Its always amusing to watch someone immediately reach up to the MCP and dial the speed back to .82 at the least 'ripple'. Relax...the airplane is built rock solid.
