Takeshi's habit of leaving large numbers of bodies as well as his Murder Is the Best Solution attitude may be due to his Envoy training.
It's never really stated whether the person involved in sleeving is "you" or just an exact replica. Indeed, the fact two copies can be active at once implies the latter. This means that Takeshi Kovacs is killed every time he's re-sleeved in a new body along with everyone else, only to be mentally cloned. Indeed, mass-murder and brainwashing a galactic scale may be taking place in the name of immortality.