It's not the reflexive I've taken an issue with, it's the verb itself. Why do the clues say "Hurt" seeing as 1) It's not accepted as an answer 2) despite offering "sårede" or "skadede", you also offered "hurt" as an option? Are the clues wrong?
I wonder at having to learn nuanced and idiomatic notions of harm and self-harm at this stage. They could of course have a respectable frequency in Danish colloquial speech, but I surely hope not; that would bring forth disturbing culture-related questions.
Im not entirely sure I understand you right, but with the self-harm theme taken up I remembered that "skadede" also is a possibility. I think that "Jeg slog mig" is used more as a "I hurt myself but it wasn't on purpose" where as "Jeg skadede mig" or "jeg skadede mig selv" would be used in association with you hurting yourself on purpose. Also seeing as the word "self-harm" is "selvskade" in danish, I would say it makes sense.. Anyway I just wanna mention, since this theme is brought up and I find it importnant to say; self harm isn't good, and I definetly dont suggest anyone trying or doing it. One will most likely find her/him self regretting it afterwards.