"even on feature phones"? It was perfectly possible at least back in the early 2000's. Where I'm from, we've gone through a lot of different IMs over the years,

"even on feature phones"? It was perfectly possible at least back in the early 2000's. Where I'm from, we've gone through a lot of different IMs over the years, including XMPP (which I was a big fan of, but started to despise because it had such terrible support for mobile clients). Many J2ME clients had pretty advanced features like group chats and file transfers.