Their permissions system and moderation tools imo outclass anyone else out there. I haven't seen parental controls but I'm curious what moderation deficiencies you're referring to.
I think the parent comment is more concerned about the prospect of young Discord users being allowed to communicate with a very large and diverse set of users/servers, which includes a lot of adult/fringe/pornographic/political content, easily allowing them to receive direct messages from others in these communities.