The author can start acting like a grown up by making enough money to fund the development or shut up. If he knew users are already paying for Slack, then obviously he can do what grown ups like Slack did to get paid users as well.
While I haven't checked for proof I wouldn't be surprised if the author is in fact spending a lot of his time not just blogging and informing about the situation, but also working on improving things.
I challenge you to do it better. Ah, screw that. I don't think you can, the way you talk. I challenge you to do something much simper: Read an RFC and try to provide interview style non-compiling code to implement it, then write a single blog post explaining what you did, applying a correct and reasonable free license to your source code and your blog post. That's something an untalented hobby programmer can do if he puts his mind to it.
I'm sure he is working on improving it. It's all in his article.
Still, he is stil "working on it". While Slack has already "delivered".
It is childish to say that whatever feature Slack has is "simply" something that can "just" be added to XMPP.
To me, the author's complaint of how Slack rips users of is the same as customer who complains when it takes month to "just" add a feature.
He himself hasn't even done it. He planned to do it, anybody can plan to do things. Anyone can be working on something that will change the world. Only few delivers. He complain about funding, while he is adding feature that he claimed was "simple".
Why does simple feature needs funding? And if Slack is ripping people of on feature that can simply be added on XMPP, then put your house on loan, create better XMPP client and earns millions of dollars. You don't need funding. That's what being adult is.
