"Is suicide a civilised act?"
Yes, insofar as it is committed by the civilised. But I wonder how the word (and concept of) "civilised" has been able to hang on to its positive connotation for so long.
"..Civilized men arrived in the Pacific, armed with alcohol, syphilis, trousers, and the Bible" (Havelock Ellis)
Moral Judgement Warning:
For Suicide:
some might feel that they had no choice to refuse life when it was given to them, so for them suicide might mean "having a choice at last".
Against Suicide:
It is very unfair to those who stay behind. It's the ones who love you that will, inevitably, feel guilty (amongst other things).