OC - if it helps with your 'terminology' the ITCZ IS an area of 'turbulent weather' which pretty much circles the globe, commonly with CB activity but generally always with 'bumps'. It may help you to Google ITCZ and see? As such, dozens if not hundreds of aircraft penetrate this 'zone' every day and nearly always experience 'turbulent weather'. Sometimes light or moderate, occasionally severe. It may be that 447 did fly into a CB - we do not yet know, but I do not see any evidence of it so far. Very few of them experience the loss of pitot systems which appear to have triggered this event so until we can establish that an 'active' CB was penetrated by them it is not really relevant.
For Saturn, I have never been to FL500 in the ITCZ so I cannot answer your question but I would expect (and not be particularly surprised by) the activity on an active ITCZ to easily produce water vapour up to FL560. It may be useful to try and look at other Sat weather images of the zone on other days. I believe it is generally accepted that the tropopause can be at FL560+ in the tropics so it should not be a surprise.