One's
bias towards their own
opinion—as a result of being the original poster, sender, or equivalent—on social media forums, especially when accompanied by a sense of self-confidence or entitlement by the sole act of sharing their
opinion on said social platform.
Why was the sender supremacist certain that the Earth is
flat? Well, it's because he sent it.
Reddit is widely considered to be the best example of sender supremacy. Either your viewpoints must entirely align with that of the sender, or you are cast off as an unknowledgeable internet
troll and promptly downvoted to
oblivion.