Can anyone explain what this 'merit' thing is? I seem to have 100, but I don't have any clue how I've obtained it

Thanks!
Have you been hiding under a rock for the last week?
https://bitcointalk.org/index.php?topic=2818350.0Edit: Sorry that was a bit harsh. I just checked your post history and it seems you were not active last week. Even so, if you check the Meta board it is absolutely chock full of threads about it.