I think quality on online platforms is really subjective. For me, a lot of it comes from the discussions or conversations a post can spark. Without that dialogue, a lot of posts feel pretty useless. That’s not to say all posts need conversation, some, especially on technical topics, don’t require it. They just provide answers. But in general, the interaction is what gives a post value.
A lot of posts I read here leave me with questions or make me want to respond, and for me, that’s probably the biggest sign of quality. But honestly, I don’t always read other people’s comments on posts. I could, but sometimes it feels like it would take too long, and I’d rather move on to other posts from people I follow. It’s more of a time thing, I just can’t read every comment, except for the ones on my own posts.