Raymarching issue with banding/clumping

I’m working on converting Milo Yip’s great light2d implementation to TD GLSL. “Basic light” works great, but when I try to implement reading emissiveness from a secondary texture I get really poor-quality output. I am not sure what’s going wrong here-- when I try adding a multiplier on the SDF accumulation I get this:

When I keep the SDF accumulation and increase brightness I get this:

My simple implementation, for comparison:

TD file:
base_light_and_dark.tox (9.5 KB)