Are you saying that every comment whose conclusion happens to right should be upvoted (or at least not downvoted)? If so, that would be a mistake. If you present bad reasons to believe correct conclusion X, you are hurting the discussion just as much as if you argued for not-X. And the reasons given in that comment (fixed quantity implies zero-sum utility over such transactions) are bad reasons to believe bitcoin is not a currency.

Furthermore, there's still the fact that the commenter was latching onto a minor, tangential point and blowing it up to be the focus of the discussion. That's also an anti-pattern.

If you want to argue that bitcoin makes for a bad currency, great! I would just encourage you to bring it up in a place where it's actually relevant to the article or comment it replies to, and do so with reasons that pass simple sanity checks.

And if you were correctly representing the Medium article, then it's still a bad argument for the reason I gave. I would recommend using a different argument, or finding a more correct point to draw from that article.

But then, as mentioned before, you were still blowing up a tangential, non-central point (whether bitcoin is "a currency"), and that still makes it an unhelpful comment, for making the point there. The comment would have communicated just about the same thing if it said, "bitcoin's value, like any financial asset, is determined by the market"; nothing in the comment was making major inferences specifically from bitcoin's status as a currency.