I said before that removing "dig/bury & upvote/downvote" aspect is what I like a lot. If a comment was well thought out, you can like it, if not just leave it alone. I think that in itself will stop the reaction gif, meme, 9gag type stuff.
I'm afraid that Hubski won't scale well enough to handle users that would "share" that sort of thing, though. Someone posts a meme or a pun that doesn't contribute to the conversation, 8 other people come "share" it, and boom, it's a top comment of a comment page. Repeat as necessary. Hubski doesn't really have anything to counter that, does it? Besides "ignore", which isn't ideal for one off-hand comment.
This is a valid concern and is one we think about. Currently, you can "hush" a user which filters their comments to the bottom of the comment thread. It's a start. But here lies the challenge, we can give all the tools you need to customize your experience and on the flipside they'll be 10 people telling us how it's going to end up creating an echo chamber and will censor people etc etc
Someone should start a meme tag and see if a memestastic hubski could exist ignored by cool folks.