Thanks for the kind words!
Stack Overflow and Quora certainly have reputation systems, and I love both sites. But I don’t feel either of them is focusing on being a hiring platform.
Stack Overflow is a great source of content, and it does provide reputation capital for the minority of its users who invest in the platform. But I haven’t seen any evidence that it’s upvoting and downvoting creates a particularly robust signal of expertise. It seems too conflated with the propensity to engage with the platform. Which is probably fine for Stack Overflow, since they want people to engage with the platform — it’s a content site. Also, reputation isn’t tied to specific skills.
I like that Quora’s reputation ecosystem is more tied to specific topics, but it’s also about popularity and engagement. Again, appropriate to a content site that wants people to engage with the platform.
So both sites are awesome, but neither is about to replace LinkedIn as a hiring platform — at least not in their current form.
And to your last point, yes, employers could be a lot better at job posting. See my Quora answer: https://www.quora.com/How-can-companies-better-source-technical-talent.