On delta.dumb, you can see the fare rules just before the purchase. Toward the bottom of the summary page, there are a couple lines that seem to be boilerplate about fees and conditions. If you click on the right word there, you're sent to a page that shows the exact fare code(s) and both summary and full fare rule links.

However, I've never found a way to see the fare rules after purchasing the ticket except on EF.