I was scammed on this thread https://bitcointalk.org/index.php?topic=1325618.msg13590577#msg13590577 which was locked.

This thread looks suspiciously simular https://bitcointalk.org/index.php?topic=1347934.0 which is also locked.

I understand there is a feedback system but it's only effective after someone gets scammed. I don't see a good reason to allow a normal user to lock topics. User input and sellers reactions may prevent a lot of scams.