If you drive through a puddle, should you slow down to avoid splashing pedestrians?

Yes, the driver of a vehicle has a duty to drive in such a way as to not splash pedestrians with water or mud. This stems from the general principle of caution and avoiding actions that could cause harm to anyone, as defined in Art. 3 para. 1 of the Road Traffic Act. Splashing a pedestrian is an offence punishable by a fine.