These maneuvers look strange because Rosetta is too far from the comet at those points for a real orbit. The probe can change course freely without the gravity

These maneuvers look strange because Rosetta is too far from the comet at those points for a real orbit. The probe can change course freely without the gravity of the comet affecting it much. The reason for the maneuvers is to maintain line of sight with the Philae lander so that communications between Earth and Philae can be relayed, hence "relay phase". Then the probe inserts itself back into an orbit.