A new habit that seems to be creeping in are drivers going right on a roundabout who, not only do they not signal their intention to leave the roundabout but they don't even cancel their indicator (why should I, the car will do it for me?).
You are waiting to join at their off route and because they are signalling you think they are continuing round. Then they come off with their right indicator still flashing. Some suddenly realise you are waiting and as they turn off they cancel their indicator. Too late, swine.
I always cancel my indicator at the previous route, as soon as there is no doubt I am continuing round, then signal my intention to leave as soon as I am abeam the previous route. Maybe I was just taught right.