Hey there! I'm the editor for Better Marketing mentioned here. To clarify, as other commenters have noted, this happens anytime anyone leaves a comment on a draft of an article. ("Watch out for this if you submit to Better Marketing" feels like a bit of a misleading title and an unfair mischaracterization, but that's just my opinion).
If a friend leaves comments on your draft to help you with your work, it'll say "Thanks to (friend's name)". I think that's the original intention of this feature, to credit folks who have helped you out in the editing process. It just also leave that comment if the comment left happens to be a rejection, which isn't great design. But it'll happen anytime you get a rejection note from any publication, not just Better Marketing (if the publication manages their rejections via private notes, that is, which many do).
As noted in your article, you can hit "hide" and it'll go away. We don't "add" them to our articles - we don't control them at all - it's an automated Medium feature.
And no, I have absolutely no connection to The Illumination.
Hope that helps!