In whatwg/html#8241 @tashasyarifah struggled to sign the Participant Agreement because they thought the triangles were bullet points of a list, and clicked the link "Individual" which doesn't expand the <details> but just scrolls up to the definition.
This is confusing UI. We shouldn't use links in <summary> (also see whatwg/html#2272), and the styling could maybe be different to make it more usable.
For example, maybe there could be a radio button group for signing as individual vs entity, and selecting the radio button expands the appropriate <details>.
Currently it looks like this:

Straw person proposal:
