Yeah that's a good point. I was trying to think of a more generic and word for 'agree' - maybe 'endorse'. I see it as a tool to be able to quickly engage in a thread when someone has made a valuable post, but you don't either have anything further to add or don't have time to add it. Likewise, I think it's useful to be able to know when people don't endorse something you have posted so you can reflect. There's obviously nothing wrong with having an idea or opinion that people disagree with, and so long as it isn't tied to magic profile points I don't see it preventing people from posting minority/controversial opinions. As you say, it's effectively a simple rating system. I personally don't like five star rating systems because I don't think they reflect human behaviour.

Here's a couple of examples. There may be a comment thread with a high child count, then with each comment below making valid counterpoints and receiving high endorsements, highlighting a great quality of conversation. Or maybe I post something creative and I get a low number of endorsements and receive various critiques below, of which one comment has very low endorsements but another has high endorsements. I can then focus my attention on the points made in the highly endorsed comment to challenge my thinking.

It would definitely need testing to see how people interact.

The space for links may encourage people not to only post links as a response. I've seen on a few occasions (not that I can see any now) where someone has just posted a link as a comment. That's fine, but I usually want to know what you think about the content in the link.