I'm not new to mums net but I am a 'lurker'. I've found reading many threads in here very interesting.
I have been teaching for 10 years at GCSE and A Level only (all exam students) and I am also an examiner for 2 different exam boards and two different subjects. I team lead a paper so examiner experience is pretty good (since 2007)
Remarks- they are done by a more senior examine - TL or PE (principal examiner) depending on subject and exam board approx 30% of exam papers are sent for remarks! Most do not change but approx 10% will change (up or down) in some cases it is because the original paper was harshly or weakly marked. Occasionally it may be a computer clerical error (most exam boards use online marking/scanned scripts)
In many cases where I HAVE awarded more marks its actually due to poor handwriting on the student's part. They are often so tricky to read that the examiner can't decipher what is being written - often then unable to apply to the mark scheme. I have more time and more experience and can often 'figure out' what is being said. I really recommend those students with tiny microscopic handwriting or poor handwriting to type!
Not every single paper is double checked so sometimes standards do slip sadly. I have to sample my team 3 times (total of 30 samples) when they mark 150 papers so some will slip through.
When having a remark the new examiner doesn't know the school/sex/background so have no idea if you've asked for a paper back too or what your teacher thinks. They simply re-apply the markscheme to the work.
As a teacher I am genuinely shocked that schools are recommending remarks without script photocopies first! It's such a risk and say the mark goes up by 2/3 and puts the student from a d to a c it still doesn't show where the student went wrong if they were expected an A grade.
It saves the parent money (or the school if they are paying) but the student learns nothing. Don't forget that UMS marks can be nearly 2 x the raw mark depending on where within the mark scale the student sits. So if it is remarked and goes from a C to a B it's probably gone up ~ 5 raw marks (depending on the original score) which is about 10 UMS marks, so it's just as easy to lose a grade as it is to gain one.