Here’s a very simple feature idea which will save many users a lot of time and avoid frustration.
Use case:
I want to be able to identify all the flags of the world, so I take the course on memrise. But like most people I already know a bunch of flags like that of my own country plus the most famous ones like the Stars and Stripes. But I have no way of telling memrise this and I have to repeat and review these items which I already know. It wastes a lot of time which I’d to spend learning the flags I don’t already know. In my case I gave up on the course because it was needlessly making me repeat these items.
Solution:
When a new item is first introduced, have a button ‘I already know this’. Then perhaps test the user on it just once to make sure they weren’t cheating, then never repeat or review it again.
Think how much time this could save a user taking a course such as ‘5000 most common German words’ who already knows a few hundred. We’re talking many hours saved. Plus I’m sure the course drop out rate will decrease because you remove the frustration/boredom of unnecessary learning.
You could create this as a pro feature - I’m a paying subscriber so wouldn’t mind 
What do you think?
Thanks for listening.
Tom