The doc comment below should be hidden from end users because the terms value and exp are not defined anywhere end users can see.

// Decimal represents a fixed-point decimal. It is immutable.
// number = value * 10 ^ exp ← (THIS)
type Decimal struct {
	value *big.Int

	// NOTE(vadim): this must be an int32, because we cast it to float64 during
	// calculations. If exp is 64 bit, we might lose precision.
	// If we cared about being able to represent every possible decimal, we
	// could make exp a *big.Int but it would hurt performance and numbers
	// like that are unrealistic.
	exp int32
}

Some suggestions:

• Prevent the line from being rendered. (I don't know it's technically possible in Go though.)

• Just move the line inside struct{ ... }. Maybe just after the opening brace {.

• Keep the comment but define the terms value and exp. I think this approach is very interesting as I was personally impressed when I first read the source code to know how Decimal was implemented.