There's @dustsweeper which can help upvoted comments climb above the dust threshold - I can honestly recommend it.

Post engagement is author's responsibility, and it is not that difficult to build up enough HP for rewarding comments (not the "cool photos bro!" style) within a couple of months since joining Hive. I don't see much space for automatization beyond Dustsweeper, which always upvotes only those comments, that have already been upvoted by somebody else.