Actually, this is because comments have been disabled across all blogs on the Diablo III community site in order to comply with GDPR. The comment system on blogs functioned off of our old forum system software, which was not GDPR friendly. In order to remain compliant, we had to disable them by the end of the year.
This was communicated in earlier blogs, including our Season 19 preview/now live and Luis Barriga’s letter to the community, and David Kim’s missed the template memo intended to be added to all future blogs because it was being handled in a different vacuum while I was addressing Season 19 launch and 2.6.7a deployment. I’ll get it added today so that that’s clearer.
As for why we aren’t commenting on other Diablo IV development questions and/or threads, there’s already a sticky in this forum explaining our stance and approach to communication regarding our in-development game. You can also join the active discussion here.
The TLDR is it’s too early.
The longer answer is we’ve only just announced; our communication will continue to come in the form of quarterly blogs, the first of which is planned for Q1 next year. We have one more System Design blog in the pipeline that you can expect before we take time off for winter break with our families; that should be coming in the next couple of weeks or so. 