Most objects appear to break when hit with a melee attack on the user's client, but typically the objects remain unbroken on the server side (and thus on other clients).

To reproduce:

  1. Melee attack a breakable object like a pot sitting on the ground
  2. Note the breakable object breaks on your client.
  3. Attempt to move into the area previously occupied by the breakable object
  4. Note that the server does not allow you to occupy the empty space
  5. Fire a ranged weapon into the space where the breakable object existed pre-melee
  6. Note that the server now allows you to occupy the area previously occupied by the breakable object

This same behavior is observed for cash registers; other players will not see/hear the register open but the melee attacker does. Windows seem to break from melee just fine.