I think you might be onto something. What examples do we have of products that purely use likes or upvotes that benefit the thing shared without benefitting the user?
For the greater good? You probably wouldn't get many 12 year olds, but that is perhaps what you want. Getting points for comments isn't really anything anyway.
Comments on YouTube and ArsTechnica have vote counts, but the count is only attached to the comment, not the user. The votes are just used for sorting.
How does the sorting work on Youtube? It's not by upvotes, it's not by date, it's not any obvious combination of the two (as newer comments with more upvotes can still be sorted after older comments with fewer upvotes). Them using a hidden total-like-count might be an explanation.
If you don't surface newer comments all the upvotes will skew towards older comments. I expect there's an element of randomness. Number of replies, whether the uploader put their badge on it or replied are probably also taken into account.