Is it safe to use phone while charging with portable powerbank?

I understand using phone while it is being charged by a normal charger is not advised. What about using phone while it is being charged by a portable charger (powerbank)? I own a HTC one and i was told by a mobile technician HTC’s own portable charger only should be used for HTC one. How much truth is there to it as HTC powerbank is not available in my city and i am thinking of using Sony portable charger for charging my HTC One?