Yes - it is likely down to the lack of a standard. Upvotes are federated out as the same ActivityPub schema as liking something. Boosts are federated out as boosts. So if someone on Mastodon saw your comment for example, liking it - is typically a way to say to the poster "I like this", but when you boost it you want other people to see it - so the sentiment is roughly the same here. Because if your reputation could be increased by someone on a different platform simply liking your comment - that would be fine - but there is no currently available federated ability to downvote - so people would have an artificially high reputation, because only the people on kBin platforms can downvote you. (I don't actually know if downvotes from lemmy platforms affect us here)