What do you mean by 'signed off'? And is that 100% confirmed fact? Is there not any non-malicious reason why someone would do that?

The only thing we, the public, know for certain is that the airplane didn't arrive at its intended destination and that we don't know where it is now. There are no other hard 100% established facts known about this mystery.

Right now the evidence leaves the door open for numerous plausible scenarios and far too many people and news outlets are fitting the evidence into pre-conceived conclusions instead of waiting to draw their conclusions after finding more hard factual evidence.