Based on what the author has written, I'm just not feeling particularly strongly here. He has a bunch of unsubstantiated claims, plus some screenshots from Blind (which I don't consider representative or reliable).

If I take what is written at face value, and assume it's true, I think it's pretty bad, but unfortunately not that remarkable or unusual. Unless he's holding back some damning evidence of actual law-breaking, I don't really see how Atlassian will be all that hurt by this.

I already wouldn't want to work for Atlassian because I think Jira and Confluence are the some of the worst products I have to use, and working on those would probably drive me to drink. Reading an unsubstantiated, biased account of their employment practices (practices which may not be "practices" but more an unfortunate one-off edge case) doesn't really move the needle much for me.