In nursing school, I was told during my psychiatric rotation (for example), that you must ask patients about thoughts of suicide to assess their risk, and by doing so, you are not implanting the idea into their minds. You are not 'giving them any ideas'. I kind of think of self-harm in the same way sometimes. I had never really thought about it, until I read of BPD and related to the diagnosis so much. I, like you, thought about SI as an option after finding out about it because if it helps other people, maybe it can help me. I think it would have probably happened eventually though, although I have no way of knowing that, and am thus constantly concerned that I put the idea in my head by relating to the BPD diagnosis.