not really. the point of rep is to provide positive rep for people whose posts are good or provide constructive feedback for people whose posts are bad. responding with those things in a normal thread would be considered spam.
But the thing is, many people don't use it for that. They use it to say whether they agree with a post or not, often without a reason. That's not constructive criticism. That's just agreeing or disagreeing with someone, and I doubt that's the same as finding a post helpful or not finding it helpful. All it does is disinclines people from being honest on this site.
Then you'll have people posting comments explaining why they gave reputation the way they did. These people often have valid explanations, but here's the thing. Nearly every comment I've gotten dealing with my reputation (where someone's actually left a valid explanation), I could respond to if it was posted in a topic. I would have a response for most of them, not to mention most would be on topic and not spam, because they have to do directly with the topic. However, not only is it impossible to respond to reputation comments, it's impossible to know who posted them. This is what makes it an escape clause to avoid discussing the topic on the forums. They can post something in the reputation comments, and there's no way to respond or know who posted it. That is why it defeats the purpose of a message board. One of the comments I got posted a question that I could have answered. I don't even know how a person asks a question as a reason for giving them reputation, but that's what happened.
But then again, there are some things which just defy explanation. 'Your feelings seem pretty accurate.' What does that even mean? It makes no sense.
The point I would make is this. It seems to me that at the very least, many people don't seem to realize what a reputation system is supposed to be used for. As you said yourself, it is supposed to be used as a form of constructive commentary, yet many people don't use it in this manner. Many people use it to simply agree or disagree with someone (like button?). And those that do use it constructively often have enough material to simply make it a post on the topic in question, causing lost opportunities for discussion.
That is the reason I suggested two ways to counter this. First, a Like button (or something similar) where people could just click it when they see a post that they find useful or that they just in general liked. Or, a character minimum for reputation comments. This would go a long way to curb a lot of what does happen (and probably also help weed out people that do abuse the system).
