I dont think "you are really awful" should be a correct translation because in English "really" has two definitions: "to great extent" or "truly," and the Esperanto word "vere" only translates to "truly" and not "to great extent."
You are really awful - Vi estas ege acxa
You really are awful, aren't you? - Vi vere estas acxa, cxu ne?
You are truly awful - vi estas vere acxa
I think using "vere" to mean "ege" is just a colloquialism carried over from English.
Well, I think "truly" kind of has the same problem that "really" has, in English. And anyway, shouldn't it be alright (at least in the context of Duolingo) so long as one of the interpretations in the English translation is the intended interpretation in the source Esperanto?
That said, it's worth pointing this out to clarify how the word is used differently between the languages, or rather, how "vere" and "really" are not perfectly equivalent.