In my opinion, default clamps, both direct and indirect, and filter glossy should be set to zero. Yes, it may cause fireflies, but otherwise it may lead to more horrible results, for example manipulation with really bright light sources, which power exceeds clamp values, will have no difference in the viewport. Some old demo files have low clamp values.
This problem is more confusing for a user to identify or describe, than just handling fireflies. Low clamp values may be described as “I do everything I can and nothing happens to my lights”, while fireflies are googled easily with a simple and obvious search request “blender bright pixels”.
And with introduction of nishita sky this issue of preset clamp values comes back in a new flavour. As I figured out in my personal tests, nishita sun disk brightness is roughly equal to sun power of 100, and the sky is dimmer by one order of magnitude, and both effectively make default clamp values absolutely useless.