Δεν θυμάμαι την διεύθυνση μου
I came across this sentence in Places, lesson 3. I would have expected a second accent, Δεν θυμάμαι την διεύθυνσή μου. Am I wrong or is it optional or what? In fact the second accent hardly ever seems to be there in this course when I would have expected it.
No, you are right and the course sentences are wrong.
They arose because you can't write arbitrary sentences on Duolingo as a course developer - you have to put them together out of words which you have already taught up to that point.
And the list includes words such as όνομα, διεύθυνση, ποδήλατο but not words such as όνομά, διεύθυνσή, ποδήλατό and so those words are not available for such sentences.
I believe course maintainers are thinking about how to solve this problem in a possible second version of the language-learning tree but it's not possible to fix it in the current one now that it is in beta.
So the correct version should always be accepted as an alternative, but it's not currently possible to change things so that the correct version becomes the primary "best" translation.