I've been using NWC for many years and this has always puzzled me. It doesn't seem to make any difference to me whether I turn it ON or OFF! For some time I've configured it to be ON since, on balance, if I have to choose between a Smart insertion point and a Dumb one, give me the Smart one!
Any ideas? The Help doesn't help at all - I've searched for "smart" without luck. Searching this forum, there seems to be some implication that it's to do with Text - and since I don't use Text very much, that's perhaps why I don't notice any difference.