I agree self-moderated topics can serve a purpose outside of the Marketplace. There was an initiative a while back where some members created all topics this way. The idea was they were going to reduce the workload on the Mods by deleting Spam and off-topic themselves. Whether you agree with them or not in discussion threads is up to you, and you can choose to post there accordingly.
The purpose of this thread is only in relation to Marketplace sections.
However, I am not fan of self moderated thread but it would change based on user rank. Self moderated thread should be disable below full member rank.
I disagree anyone has the capacity to use it properly or abuse it, irregardless of rank. That's why I like the idea of needing to be whitelisted. The requirement might be your account needs to have enough substance a Mod can make a determination on whether you need it or not; or if it's a net benefit to allow someone to use it.