Once again lets talk about white spot. [:)]

At the opposite, I tend to think that the current settings render objects too shiny very often, and wonder if I shouldn't reduce at least default shininess to a much lower value.

See the below image render in SH3D

and here is some test results render in sunflow 0.7.2. Comparing these images in different lights and shader settings.
1. Gi ambocc only
2. Sunsky light only
3. Ambocc+Sunsky
4. Ambocc+Sunsky+IBL
5. Here phong,shiny and mirror shaders produces different reflection when using ambocc+sunsky
(lower than one reflection does not produce white spot).

increasing reflection one to ten
again increasing reflection ten to fifty
6. Phong reflection is works in SH3D so comparing this shader in different values
and the same reflection produced in SH3D
[Reflection is smoother because SH3D AA 1,2 and sunflow AA 0,0. Also gi path/ambocc +sunsky+ ibl+ point light(fake sun)]
Conclusion: in phong shader reflection lies in between zero and one.

Sunflow wiki manual(page17) says we can go beyond one for the reflection but will produce strange issues.
I think it can be solved by switching through shaders in background when increasing reflection slider.
ie: Start with diffuse then phong at spec 0.01 to 10 then switch to shiny reflection 0.1 to 1 then mirror shader 0.2 to 1 while increasing shininess slider. [:-?]
I hope, I explained it correctly.