To be honest, I don't think the HP answer takes it any further. We already knew a standard micro-USB cable could charge it - that was part of the appeal.
The trouble is, the standard micro-USB is too low-powered to charge it while it's being used - it can barely maintain the existing charge while the computer is switched on, and a typical 1amp USB cable will take up to 12 hours to charge it. It's really an emergency thing.
The official charger is a 3amp, 5.25v thing and will charge it in about 4 hours, which is practical. As I said at the start, it would be good to have some sort of commentary from HP about what the problem is and when they expect a fix.
But as I also said, my charger appears to be working and isn't heating up too much.
