Sorry, wall o text. 
TL;DR
Reputation systems have value outside of just Q&A sites.
They can add a lot of meaning to discussions, as they change how readers perceive the relative worth of discussion participants. This can provide additional context to exchanges between users, context that might be inherently understood by existing members but not by new members and guests.
Longer Version
I’ve been using Discourse for awhile and love it, but it’s extremely awkward with how it rewards participation. Specifically because badges are used instead of a much simpler reputation metric.
Speaking just for myself, I just created my account here and within the first several minutes I’ve already received 2 badges; one for reaching level 1 and one for liking a post the first time. At the risk of sounding rude, these feel utterly meaningless.
It’s like when you play an online game and get a trophy for killing your first enemy of thousands more to come. It feels more like checking a box than any sort of reflection of social capital. Getting these early badges didn’t encourage me to interact with this sytem, they gave me the perception that badges have little worth and therefore are of little interest to me. “Oh, I got another badge. K.”
I understand the hesitance to encourage the gaming of discussion, but I wonder why bother with the badges at all, then? I myself have about 30 in the main forum I run and couldn’t you what they are without looking. I honestly don’t care about them, nor do many of my users.
On the other hand, something like reputation allows readers the ability gauge a user’s value to the community relative to other users within a single thread. This not only gives a conversation more depth, it also rewards users more visibly. I don’t know about the rest of you all but I rarely actually click a username to see their badges. I read their post and move on. Perhaps that’s by design, but there’s a missed opportunity to represent nuance in a conversation via a simple metric attached to its participants.
It’s an apt metaphor for conversations in real life. When you’re in a group conversation, you can often infer subtle but significant things about people independent of the words they actually use. Things like confidence and social standing within the group. Literal reputation. This gives a conversation a life of its own outside of its transcript.
The benefit to this isn’t limited to Q&A or reddit type sites. There’s a valid use for this within discussion software as well. I want to quickly know the relative value of users’ words against each other. Badges do not provide this. Trust levels do not provide this. Reputation does provide this.
@codinghorror said something here that caught my eye:
I don’t think “proving an opinion” is the goal. Rather, the goal is gauging a user’s value to the community quickly and within a single thread and against other users. It’s not just for vanity either; this has an impact on readers’ perception of an author’s message within the context of the community’s larger focus. This is valuable information that is deliberately ignored right now.
Something else caught my eye here from @Stephen:
Discourse’s badges are indeed flexible, but they are also overwhelming and noisy. Upvotes (and reputation) are indeed crude, but they are also simple and intuitive.
That said, I understand Discourse’s direction and am still thankful for it (and its plugin system!). I hope though that people might come to understand why reputation is more than just meaningless internet points, and that it has value outside of the Q&A format.
Edit: immediately after I posted this:
And reputation is the feature of dubious value? 
I still love Discourse, but I don’t understand the prevailing perspective on this matter. 