Real talk though. I'm calling bullshit. This guy has very few posts, and seems to only post in small spurts every few weeks. A little over 1/3rd of his posts are him being excessively pissed at the people on the NerdCubed podcast, and most of the rest are obsession with /r/emboldenthee, and his (dumb) pet theory about how it was made by an alternate account (suspicious...). The assumption that he's randomly on such a weird subreddit is out there, but MAYBE she was looking over his shoulder when he found this place or whatever randomly.

However, the woman in this situation doesn't have a single post, and is a completely new account. How could he know that it was her? The account was specifically made for this post. Plus the generic name "mark" is so non specific, I doubt it would be anyone's assumption that they were talking about them. Mark here would almost certainly have to have prior knowledge about this.

Honestly, BEST CASE scenario that I can come up with is that they, for whatever reason AFTER getting proposed decided to do a fake thing on reddit about it, which is weird because they both seemingly so obviously don't care much about reddit.

Thus, the more obvious solution is that the entire thing is faked by 1 guy who was bored.