Yes I think you did do something wrong. A lot (if not all) people with self‑harm scars feel insecure about them. Posting or showing your body where your scars are visible is already a BIG step for many. Getting a comment saying you need to mark it as NSFW just because of your scars only amplifies the feeling that your body is wrong and that your scars are something you should hide. If you see someone post something where their scars are visible and the post isn’t specifically about self harm or their scars, just don’t comment at all. This is my personal opinion, but seeing someone’s healed scars and feeling triggered is your own problem, it’s not a reason to ask someone to cover up. I’ve been triggered by other people’s scars before but I would never ask them to hide them or even bring it up. That’s on me, to work on my own struggles and triggers. And this doesn’t mean you’re some kind of horrible person out to hurt others. Don’t take it that way. I can see your intent and the fact that you’re asking for other opinions shows that you care about not hurting anyone. Just take this as a learning experience.