Hi Bachus:

I admire your honesty and strength of character. Your question has many variables, making it difficult to offer an applicable reply. Would I buy a knowingly damaged Keyboard? It depends on why I wanted it. (Use it for parts, have the skills to repair it myself... or have access to someone who does, believe the damage is so minor it would not affect it's playability, and the list goes on.)

Good luck, not matter the reason. Personally, I would always investigate (if possible, to understand the damage) then negotiate to make the potential risk more palatable... unless the "deal" is too good to refuse.