Chat apps like whatsapp can be helpful for communities, especially for more organized meetings or question-answer calls or video presentations to have a live-chat with that can be good. It is different than a forum platform such as Discourse where people may seem more distant, as there can be a delay from when someone posts something to when anyone reads or replies of a few days.
However with Discourse specifically since this runs fairly fast and has features such as displaying if someone is writing a reply, it is already close to being in the same category as whats-app or sms texting because of that.