More specifically, the Washington Post informs that Instagram is considering to give its users self-moderate comments under their own account. At least if you are concerned about the number of "leftist" comments, which for you is not particularly important, you can leaving your profile public, to prohibit commenting.
Sometimes we have to hear from friends, just hanging out in Instagram that they are not particularly happy with the dominance of different stores in social networks. They say, will mark a picture of something, immediately fly likes and comments, but not from living people, but from bots or just a promotional ad accounts that actually care about your photos, but in this way they attract attention to themselves by promoting their own product. Rumor has it that soon the situation may change ;)