[dang]

> I'm not sure why it's OK for this poster to claim

It may not be. We (I'm a moderator here) try to be consistent, but it's impossible for us to see everything, let alone consider it all carefully.

The trouble with your comment was that it went straight to name-calling ("stupid and slanderous"), when it should have provided information. Your final paragraph above, the one that begins "Here's the problem", is much better. It's an informative expression of what lies behind your defense of Udemy and makes a fine contribution to the thread.

HN can be a cryptic place sometimes and I apologize if it felt like we were picking on you personally. That was not my intention. It's entirely fair for you to stand up for Udemy based on your experience. But to be a good HN citizen, please do so informatively and neutrally, even when other commenters say unfair things.