According to commits in this HN thread, including the one you're replying to (which I have not independently verified), that Reddit post is factually mistaken about crucial points. There is no reason to be alarmed, to worry about the certificate, or try to disable it.

There may be some merit to the point about running the local permanent HTTPS server but that's unrelated to the certificate.

I tried to expand this comment to include a technical explanation of the issues, but it became quite long. I'll try to simplify and summarize: there are legitimate security concerns about applications that install their own Certificate Authorities (CAs, aka root certificates), especially when the same one is being installed on all computers. A Certificate Authority has the ability to issue certificates for any website, so it has the ability to compromise the user's traffic to any website if mismanaged. Blizzard didn't do that. Blizzard installs a randomly generated, unique-to-the-user certificate (not certificate authority) for Blizzard's own website domain name. This does not present any of the security issues alleged by the Reddit comment.

So there is no root certificate or CA involved -- the title of this HN article is incorrect and the Reddit thread is mistaken. (To caveat again: I have not personally verified this, and am digesting information supplied by other HNers) However, if you don't plan to log in to Battle.net using Facebook, then there's probably no downside to disabling this certificate either.