I am with Jocko and hate the way when you use normal indicators to go around a corner and they self cancel you very often find that the stalk has gone far enough the other way to put the opposite indicator on for 3 blinks (just as you straighten up from one corner your indicators tell other road users you are turning the other way WTF ! ).
I have never experienced this!
Sounds dangerous, perhaps something needs adjusting?
Not seen this once in over 30,000 miles. I like the 3 flash mechanism (but agree it should probably be 4), it has been fitted to a lot of cars for several years now. I also indicate every time, even if I think the road is clear. I was taught that way for good reason. The time you miss seeing something is when you will cause an crash.
Unfortunately most people who haven't been through an advanced driving course misunderstand this advice. They seem to think that it's an attempt to 'save effort' or perhaps to prolong the life of the indicator bulbs, and it isn't. 'Not indicating when it isn't needed' is a poor way of explaining it which is perhaps where the confusion comes from.
The reasoning behind it is that before you execute a maneuver you should ensure that you are fully aware of your surroundings and other road users. If that leads you to conclude that no-one would benefit from your indication then don't bother doing it. Why would you? The only reason in that scenario would be if, after performing your check, you weren't sure. In that case you shouldn't execute the maneuver.
Another problem is that people can get into the habit of 'indicate and go' without properly assessing what's around them. The purpose of this advice is to encourage drivers to indicate because someone needs to know what they are doing rather than out of habit.
There is also an element of minimising distractions. Indicators are designed to catch the eye so an unnecessary indication is a distraction and distractions cause accidents.
In practice I find that it's rare on today's busy roads for an indicator not to be required but on dual carriageways and motorways it's still often superfluous.