imho coming back under a different name is bordering on fraudulent
I think that some posters worry that they have revealed too much of themselves and could be recognisable to friends, family - particularly now they realise threads are linked on FB and Twitter.
Several members seem to have despaired of ever having a proper, objective discussion on this thread.
Surely no poster would disappear because they thought there could not be a 'proper, objective discussion' on any particular thread. If so, just avoid that particular thread surely?
I don't believe that for a minute, particularly the posters jura mentioned in the OP - they are more robust than that!
Perhaps they are on holiday/taking a break/looking after GC, there could be many reasons.