Unless you have a relevant trademark, there isn't really much you can do here You can rant about it and get that rant read by people who make branding decision

Unless you have a relevant trademark, there isn't really much you can do here You can rant about it and get that rant read by people who make branding decisions. And sometime in the future someone may say something like "even though there's nothing legal stopping us from re-using this person's existing reasonably well-established online identity, there may be negative consequences, so maybe we should keep looking" The charge is rudeness, not IP or Trademark violation. A community addresses rudeness by calling it out.