I would strongly advise not touching anything there until the clearHDR changes get merged into the master for 1.1 and THEN making an assessment about whether things are too bright or not because the HDR brightness values have all been tweaked to remove that nasty glare issue in clear weather.
Even without HDR or Bloom, the interior areas can be too bright on a clear day. I don't use either and I've noticed it.
Reducing the RGB values by 32 will make nearly all indoor areas dark, even in daylight, which is simply ludicrous.
You're mistaken. I've reduced them by 48 and it's just about right now. I'm only referring to the Sunlight values here, not the Ambient values. That's what causing the issue. They're far too high for an interior space, they're exactly the same as the values for the outside weather, and exactly the same as the vanilla values. It's the same for both indoors and outdoors for all clear weather types, nobody has made any changes to the default Sunlight values.
PS: Some examples:
MTClear01:
R: 255
G: 241
B: 223
InteriorMTClear01:
R: 255
G: 241
B: 223
Vanilla:
R: 255
G: 241
B: 223
Those values are high enough that they'll have a considerable impact on an interior scene, it's getting close to pure white, and there's lots of room for lowering them. I suspect that no one has thought about how much of an impact the Sunlight values can have on the game's lighting. It can be pretty substantial not just on the overall level but on the colour of a scene as well. It plays just as much of a role as the Ambient values do, if not more so.
PS: Try these values for interior clear Sunlight, they're working pretty good for my game so far:
R: 192
G: 160
B: 112
I prefer a warmer colour so you might not find the red to be what you want to see.