I made a mistake with a configuration entry and I cannot think of a reason that it would be useful to be able to this. I created duplicate lines within the same mqtt entry for the payload_on setting with two different values. It would make sense to detect duplicate settings for a given integration in the configuration check for the case that only one is possible. The result of the switch configuration below is that it showed as always “On”, for either state of the switch.
- platform: mqtt