Thanks ! For now I haven't looked much at "going the other way". I think it's possible as Instagram has an API that allows that kind of thing (from Steem to Instagram). For Share2Steem (and the way Instagram -> Steem) I don't use it, as the limit rates aren't good enough for what we do.
Importing likes and comments could be possible but only for people who have a Steem account and linked with Share2Steem (or else it would be illegal I think as we don't have their "permission" to broadcast their publications / likes somewhere else).