@Bloggs --
But I don't think an updraught, in itself, will cause a pitchup;
?? A severe enough updraft will cause pitchup simply from differential vertical wind speeds between wings/nose and tail.
(But excellent points on "forgetting to remember trim" and "HMI is for the H and not the M".)
Also I am assuming at minimum an automation dropout (if not an outright counter-safety automation action) in AirAsia, until FDR data shows otherwise. (Too much similarity to other such instances.)
@fireflybob -- Remember that in this case they were in mid-climb already, presumably via automation, so I am not getting where you say "selected altitude" by itself would result in "lowered attitude"?