I've just added at the suggestion of the team: Είμαι θλιμμένος γιατί το μπουφάν δεν μου κάνει and yes the period is missing I'll have to redo it but am waiting for feedback. How does it sound? Ok, it's not world class literature but the meaning comes across. No? We are very restricted to the edits we make. Your input is always appreciated. P.S. We'll delete the other as soon as we're sure of the new sentence.
Είμαι θλιμμένος γιατί το μπουφάν δεν μου κάνει sounds better, but it is still a little unnatural, I think. In my mind, I have θλιμμένος and the related words θλίψη, θλίβομαι associated with more profound causes of sadness, such as death (you may be familiar with the expression τεθλιμμένη χήρα) or disappointment ("Η σημερινή κοινωνία με θλίβει", "Θλίβομαι για λογαριασμό σου" are sentences I would use), etc. So, I would counter-propose "Είμαι θλιμμένη/ος γιατί ο πατέρας μου είναι άρρωστος" to convey this deeper meaning.
Another point: I understand that past participles are morphologically totally like adjectives (part of why they are called participles in the first place), but wouldn't it be better to teach them separately? My main argument for this is that you could use the meaning of the verb (θλίβομαι = to grief, to be sad) to make clear that θλιμμένος is not someone/something that provokes sadness (such as θλιβερός, which is the actual adjective), but rather someone who feels sad, someone saddened (past participle).
Of course, I agree with you but it's the nature of the course that changes are much harder than composing the original sentences. We are limited to only a small vocabulary. Let's see if we can do better here. Your suggestions are so much richer and closer to the meaning. Having a Skill devoted to participles is so enticing it would have been possible before we were in Beta but isn't now. Ok, I'll get on it and thank you very much.
You're welcome. You have done a wonderful job creating this course and now we are talking about small details. I also understand the reluctance of the program to change.
For all your effort, here is a favourite song of mine that includes the word θλίψη: