Discourse 更新后删除了 1500 名两年未见的 inactive 用户

These reasons all make sense and I have no issue with the removal of such accounts. It seems to me the real issue on this topic is that users feel they haven’t been informed of this change. I’m not sure if this was actually in 2.3.0beta8 but if it was, it’s not in the release notes (And yeah, if you’re on beta you’d better always check those notes before upgrading).