CHAT DO YO

I joined my own chat and why does chat messages have previews and drafts and i have to press the button to send a message.

previews

That's because formatting is via CommonMark, which ... maybe not everyone knows how the resulting text will look.
Some time later, there'll be an optional Rich Text editor, and then no need for a preview.

You can press Ctrl+Enter to post the message. That's how the editor works in the other topics, and I find that unless the chat works in the same way, I personally get confused (and at least one other person) and accidentally send messages too soon. — So it's a bit different from Slack.

Maybe there could be a Ctlr+Enter help text, ... otherwise not easy to know.

Drafts: If you start typing at home, say, then power off the computer. And want to continue composing the message at work — possibly at a different computer.