I think that's an interesting question and a tough one to answer. Essentially, I'd say it depends on those who find the subreddit. It seems to me that there are a large number of Redditors or former Redditors who have recently joined Hubski because of a r/TheoryofReddit post which was also linked in r/BestOf. This indicates that for some reason, Reddit isn't meeting all of their needs.

Of course, it's silly to assume one website or even one aggregator is going to meet 100% of a person's internet needs. But, on the other hand, it's not uncommon for Redditors and/or former Redditors to complain about what Reddit is now. Since Reddit's content is determined by its users, any complaint about content is as much a complaint about its users. And any complaint about comments is pretty directly a complaint about users. So, I think it's reasonable to think that if you have a problem with Reddit it's because of the users. So, a ton of Redditors finding/discovering Hubski and joining could lead to an influx of undesirable content.

I do think that this can be mitigated by a couple of factors, like the users of Reddit who enjoy inane/offensive/pointless comments and/or content probably won't find much to entertain themselves here. (For the moment.) Moreover if you're happy with Reddit's content why join Hubski - so it's more likely that Hubski is going to get less of the truly, purely inane Redditors that mostly generate memepics or ragecomics or what-have-you, at least for the time being. But, having an r/hubski and a random button on Reddit will contribute to some sort of (albeit small) Eternal September effect.

It can be good for Hubski for users who contribute valuable content to find it[Hubski] (perhaps from Reddit, perhaps from anywhere else) but it can also be bad for Hubski if there is an influx of users who degrade the original content. It's also worth noting, though, that unhappy users who think that the content is degrading are probably going to appear starting on Day 2 (this happened with Reddit) and it also depends on what you want Hubski to be. If the masses are happy with memepics, then they're going to be happy with an aggregator with lots of those. Personally, I'm looking for interesting articles and discussion about topics I'm interested in, not stuff like r/funny, what r/politics is, or r/AdviceAnimals. (&c.)