Er, I was spreading an idea that was someone else's. That's what posts are. Would you rather it were a post instead of a comment? Or if I linked to a webpage with the quote? Or an essay instead of a sentence? Or if I added my own commentary? "I agree with and find insightful what Clarke said." I thought that was implied.
I could have said "It's scary to think aliens might exist, but it's also scary to think that we could be alone (Clarke said something to the same effect)." But that seems unnecessary and verbose to me.
It's not truly adding to the conversation.
What adds to the conversation is entirely relative. I don't think lots of things add to conversation. I don't share those things.
I personally love quotes; I think they're great, succinct ways to condense and share big ideas.
The point of a forum like Hubski
You're assuming everyone else shares your values. Everyone is different, and thinks differently, and values different things. And that's okay. People typically express this on hubski by simply not sharing what they don't value, and following those whose values align with theirs.
Incidentally, it sounds like you might prefer to filter https://hubski.com/tag?id=quotesporn