As the privites Keys are yours and they are on your computer used to access the remote server, why not? ( you dont send your keys over the network)
So, if you have a full client then you see the whole blockchain and can harvest locally.
If you have a lightweight client then you don't see the whole blockchain and can harvest only by signing data received from remote server(s).
And now imagine that network is sybil-attacked and the attacker can trick you into harvesting on a fork...