According to a leaked Reddit moderators Slack chat right after his editing spree, he turned off PMs for mentions a long time ago.
And I thought that I work in an unprofessional company on a useless project. I feel a lot better now.
This reads like a chatlog from minecraft server for teenagers.
But yes, it's pretty awful and highly unprofessional. spez's comments in the chat are unprofessional and concerning as well.