> Slack/Discord/whatever: they are proprietary, they are closed-source, they are bad.
> IRCCloud (which is proprietary, closed source etc.): oh, it's so good, use it.
Who exactly is "HN"? How did you even decide "HN" has opinion X or Y?
I'm fine with Discord because its mostly used for gaming. Given the previous options (Ventrilo, TeamSpeak, Mumble, Skype), it is miles better. And of these, only Mumble is fully FOSS. A clear disadvantage is however privacy-related, but for gaming that isn't a huge issue.
What I'm not fine with is being forced to use Slack for work-related material. You don't want such sensitive data centralized. You want to host such yourself, or have the private keys yourself.
IRCCloud, whatever it is, probably does not have the same amount of users as the previously mentioned two. But if it uses the IRC protocol (which the name suggests), at least that is open and there's no vendor lock-in like with Slack/Discord. Which, given that Slack is used for commercial endeavors, is worse for Slack.