I work in a special needs school for children with SEBD (Social, Educational and Behavioural Difficulties) and needless to say the children always want to get the last word in a discussion, debate or argument. One useful way of letting them get the last word without losing face is to declare, at an appropriate time that, “I’m going to let you have the last word” and being silent after the last reply.
I can’t help that think the same principle applies to talking in the pub, park, on message boards and elsewhere where people have made their point and have nothing further to comment other than get in the last word.
If this is the case, perhaps we should type “I’m going to let you have the last word” more often and get in pointless arguments less often. After all, no-one will remember who had the last word next week.