The issue with auto-accept is that it effectively allows you to have multiple tries at an answer, since if I type an answer and it doesn’t get accepted, I know it’s wrong. In my opinion, that significantly decreases the efficiency of learning.
I had a userscript installed that disabled that feature, but it doesn’t work anymore with the changes on the front-end. Will it be possible to switch that feature off?
Hmmm, blanket deactivation of that function could get tricky when you consider synonyms. I personally find the auto-accept necessary because I am taking so many courses and learning so much vocabulary that I often have to try four or five different German words with the same one or two word definition listed on Memrise before I know which specific word it is asking me for (ex: sorgen, sich kümmern um, betreuen, aufpassen, pflegen, etc all essentially meaning “care for/to”), and I would lose my mind if I simply had to guess which one (and inevitably get it wrong all the time). However, I definitely understand the desire to be able to turn it off. It would make declension and conjugation courses more effective, that’s for sure. 
*Also, I know you weren’t suggesting completely getting rid of it. Just saying even a script wouldn’t work for me, because of the reasons above.)