Easy Street
I think you may be reading too much into the western/eastern taboo stuff. I'm a researcher and investigator. It's my job to ask questions, to find answers, to be objective and analytical. It's also my job not to jump to conclusions (tempting though it is and interesting as theorizing is). Evidence, sound, solid evidence is required. From an investigation perspective it's folly to theorize and try to have evidence fit the theory. At this stage (I think my preface in my OP made that clear) we have no solid evidence for a suicide theory. That does not dismiss the possibility, but it would be entirely wrong to jump to the conclusion that this is the cause based on nothing much, which some have done.
Whatever happened happened just 4 minutes into the flight, still climbing, when both pilots must have been in the cockpit (who knows of a pilot leaving the cockpit at this point?). The suicidal pilot would either need to be on their own (highly unlikely 4 minutes into the flight unless the other pilot got a sudden attack of the runs) or have incapacitated the other pilot (how when presumably the crew will have passed through security meaning knives or guns should have been picked up - even at Jakarta?), or both pilots would need to be in cahoots (really???). If the incident had occurred at cruising altitude, when the other pilot might have left the cockpit, the probability might be somewhat higher.
If you do want to put a probability percentage on suicide at the cause, given what we know so far, it wouldn't score very highly. Not because it's "taboo", but because other possible causes, given the circumstances, are more likely.
But this is all theorizing atm. We won't have to wait too long for the CVR and FDR to hopefully provide all the answers.