Mono

One channel, sent to both ears the same. A single voice has no position to convey, so mono is the right container for it. Interfaces are where this goes wrong. Plug a microphone into input one, record a stereo file, and the voice lands in the left channel only. It sounds fine on the speakers in the room and awful to anybody wearing headphones on a train. Either record a mono track or fold the file down to centre before publishing.