That’s what they call the “in-browser keyboard”. It’s intended to supplement your own keyboard so that you can easily insert the special characters (for example the accented letters etc) where they are required in your typed answer.
Where the course creator has added the in-browser keyboard, you don’t get the selection of non-special characters which Memrise recently added to courses (explained here:Memrise Release Notes - 28 Nov 2017 (Update on changes to typing test) …which many of us think is a good thing.