New answers tagged tones
The reversed tone letter is apparently one of the Modifier Tone Letters which do indeed indicate tone sandhi. I haven't yet come up with a pdf, but hazarding a guess, perhaps ˩˧ (low rising) is the recitation form and the reversed form is the sandhi form (low falling).
˩˧ is a contraction for ˩ ˧, that is an extra low tone followed by a mid tone. Similarly, ˧˩ is ˧ ˩, a mid tone followed by an extra low tone. Such tone combinations exist in Hmong. https://en.wikipedia.org/wiki/Tone_letter https://en.wikipedia.org/wiki/Hmong_language
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