Spaw, seriously, I've noticed some people respond to what they want to and ignore the rest. Politicians do too - they answer the questions they'd rather have been asked. If they talk enough, no one notices they avoided the subject. (Yeah, right.)

Re your last paragraph - did I do that? I frequently do do that. Good argument going, somebody gets upset by someone else's method of argument, somebody else gets upset by that person getting upset, then a bunch of other people upset, and somebody else gets upset because everyone else is upset, and..."thread blown all to hell." (I'm usually in there at stage 4, although this time I inadveretently managed stage 2.)