[no_circuit]

That's correct, the example you are giving represents bike-shedding among request path variations.

I assumed most readers of my comment would get that the idea that /users/signup is ambiguous whether or not that is supposed to be another resource, while /users:signup is less so.

[rendall]

It's not ambiguous that api/users/signup refers to a resource. One of the constraints of REST is that endpoints refer to resources.