My answer, "an amazing neighbour" was marked incorrect. For a company that promotes international languages not to recognize British spelling is substandard.
The course is in Beta. They will make changes based upon our feedback. There is a place to report problems and there probably will be a block to check in the future that says "My answer should be accepted." I wouldn't be so harsh. This is an American Company. Memrise is an English company where one can learn languages. It uses British spelling. But, it made changes to accept American spelling for answers based on student feedback, just as Duolingo will for British spellings.