The autohide after a visit is interesting. It might be worthy of an settings option. That said, we are keen on supporting a slower pace of consumption. As for "voting without sharing", it's intentional that everything is shared or not. The consideration that the consequence of sharing requires is exactly what we want to encourage. If it's not worth sharing, then it simply is not. Interestingly, we frequently have posts that have very many comments and few shares; but, eventually they are shared for the discussion that occurred, rather than the content of the post itself.
To be honest, I think the "hide" for each post on the feed is sufficient. Implementing an autohide feature, even if it's something you have to turn on, could result in people having difficulty finding posts they want to go back to, to converse on.