I don't know about trust. I see its key purpose as attaching (a more significant) cost to posting. Which will reduce spam that cannot extract more than it has to pay.

So it's less about trust and more about making low-returning spam a negative investment. It's about incentives, not trust.

Trust may or may not be a downstream effect from that. I haven't thought deeply enough about whether or not I trust posters here more than other places because of pay-to-post. I feel I see less noise and more signal here. But SN certainly isn't devoid of noise.