GBO:
So am I. I was an airline pilot (which included flying the B777) for nearly 40 years (gulp) with 75% of this time being involved in the Check and Training world. I'm not attempting a "mine's bigger than yours" exercise here, merely laying out my background/exposure to the realities of airline flying. Dare I ask, without resorting to "playing the man", just what operational experience do you have? Some of your responses show ignorance of the realities of operating an airline aircraft.
For instance:
Diverting to an airport 30 minutes away and purposely choosing to use heading mode over LNAV for the entire leg does not happen regularly.
It would be a poor decision and increase crew workload.
Rubbish! If an immediate return is required, then most crews that I've observed would use HDG, then sort out the return track and LNAV later. Pushing the heading knob and then rotating it hardly increases the crew workload.
You also insist, presumably because this fits your hypothesis, that the crew would have diverted to Penang, and not returned to KL. Your critique of my suggestion that's there's more than an even chance that the crew would not have selected Penang shows a lack of appreciation of the realities:
So you are diverting from IGARI to Kuala Lumpur without a serviceable radio, to an airport further away, with more traffic and higher risk of collision. Seems like a dumb decision.
Penang is closer, has a lot less traffic, familiar to the crew and open.
How much further away? A mere 60 nm by my quick calculation (i.e. 8 minutes in cruise). At this point none of your mooted failures were time critical. Are you seriously suggesting that "more traffic" is a valid reason for not selecting KL? Isn't that what surveillance radar is for? Would Penang even have been open that late (from my experience not, but that was a long time ago)? You state elsewhere that the crew would have been familiar with Penang, but arguably not recently - did MAS ever operate the B777 there? Certainly in my last airline, Penang had a reputation of being "tricky".
There are attractions for proceeding to KL. This was "Home Base", with major maintenance facilities, sufficient facilities to handle (and if necessary accommodate) a B777-load of passengers and a likely location of a replacement aircraft to continue the service. Further if the crew are stood down then they're going home to their own beds. In the theoretical world, none of these commercial/personal factors should influence command decisions but if you think that they don't (and from observation MAS crews are very eager to "help" their airline) then you're not living in the real world.