Watermelon rind can be handled as food waste or a compost ingredient. A gardening article should not present household rind recipes as treatment for illnesses.
A rind is not a medicine claim
Watermelon rind is food-related material and a possible plant-scrap input for an appropriate composting system. That does not establish that a household preparation treats colds or other illnesses. The old medical promises should not guide its use.
Separate kitchen and garden handling
Use a reliable food source and preparation method for anything intended to be eaten. Keep garden residues, treatments and compost equipment separate from food preparation. Discard questionable material using an appropriate waste route.
Composting takes management
Cutting suitable scraps smaller can help a managed pile handle them, but a wet pile of rind is not finished compost. Maintain the system according to its guidance and use the mature result appropriately. Do not pour an uncontrolled rind soak into houseplants as a complete fertilizer.
Related reading: Improving Soil Fertility: Compost and Measured Inputs.