[_nalply]

It seems people want a way to express emotion in something like a side-channel. Interpunction is fine for that, however we can't pronounce interpunction by itself and second interpunction can be placed only at specific points in the sentence (usually at the end). Emoji can be placed everywhere, however emojis can't be spoken out loud.

Lojban, a constructed language, has a very interesting feature: attitudinals: https://en.wikibooks.org/wiki/Lojban/Attitudinals

An example from Wikipedia:

mlatu .ui (a cat! yay!)

English has also attitudinals however they belong to informal speech.