I have scars and I'm perfectly stable and understand it more than those who don't SI, and would not shy away from someone in real life who SIs. However, if I were a therapist I would not disclose it to clients. Allowing your scars to show IS disclosure and I do think that can be helpful, but only much later on after a relationship has been established and you really know your client.

Besides the other things mentioned, one to also think about is the admiration many clients have for their therapists. What if the scars of a therapist were seen as approval of SI, or just the nudge needed to give a client courage or permission to do that? Even old scars could be seen as permission or approval, rather than a badge of honor for having conquered the habit.

I absolutely would keep them covered and if somewhere down the line you get to truly know a client and believe them knowing would help them and not harm them, I would think about TELLING them you used to SI, but I still would not show the scars. I did out and out ask my T if she ever used drugs or alcohol or cutting to cope with the issues she told me about and she said no but she wished she had! She was also never concerned with my cutting and felt it was simply a coping mechanism that I used very carefully. If ever I wanted to stop she said she was happy to tackle it, but if not that was fine, too.