This is what courts are for. There is no exact line because many situations are different.
Surely you don't have to have a big red cancel button on every page of your platform
Why not?
Some examples would be helpful
The text you quoted is clear enough to me, and it's probably clear to any reasonable person (most rules are written this way). If you're worried about gaming the system to find the exact process that just on the "legal" side of things, you probably aren't reasonable.