I have a constant combinator hooked up to a MLC input, sending 1 coal.

When I do nothing but out["coal"] = 1, the only thing shown in the MLC's wire signal list is [out] coal = 1. No inputs are shown.

If I change the input to 10 coal (while keeping the output as 1 coal), then 9 coal shows as an input. This can happen for green, or red, or both.

It seems to be: wrong_input = correct_input - correct_output

This is only a gui problem.

Although this does create an inadvertent feature. When the output is always updated to the what ever the current input is, if the input stays the same it will be canceled out and not shown in the gui. However if the input changes, the gui will show the difference from when the last time the output was updated, So kinda works as a rate indicator.

Huh, that's weird, as they should be fetched entirely separately from diff combinators even. Forgot to check this in 0.0.29.

Oh wow, I had res[sig_name] = sig.count - (output[sig_name] or 0) in the code counting input signals from back when this mod used constant combinator, what the hell...
(it makes sense to do this when input leads = output leads, to tell one signal from the other, but that's not the case for a while now)

Fixed in 0.0.30. Thanks again, it was a really old bug in plain sight.
I think "rate indicator" should be easy enough to setup in globals and monitor in Ctrl-F window.