The other day, I was having a conversation with someone over social media. Bear with me, because I'm about to stray into conversation analysis and this is so far out of my area it might as well be cell biology.
Conversations are prototypically turn-taking exercises, with A saying something, B responding, A responding to that, and so on. But obviously this isn't always (or even usually) the way - we interrupt each other, talk over each other, don't finish our sentences, and so on. Another thing we often do is talk for an extended length of time because we have a long story to tell or whatever. When we do this, the other person typically nods, makes encouraging noises, smiles, and generally lets the speaker know they're still listening. But in a text conversation you can't do this. If you try and do it, the little symbol that shows you're typing can put off your interlocutor because they think you're saying something meaningful, and they might stop telling their story. But if you don't, might they think you've gone off somewhere or fallen asleep or lost interest? We need a button that just sends an 'mh-hmh' symbol to show we are still there and paying attention. These are called 'acknowledgement tokens', and we need a text version.