No, that's not it. We're talking about posts like "we had a silly little quarrel about something that would need fifteen minutes to clear up and make both happy if we both just try to adult a bit" and commenters being adamant that deleting gym and facebooking up and so on is clearly the only choice. Most of said commenters probably not being in any position to give advice on relationships to others.

I see this being said often but I don't understand.

A lot of people posting there are young and may well be in their first relationship. It makes sense for them to ask a question in the community they spend their most time in - which is reddit

Most people overshare on reddit and it's completely unrelated to the seriousness of the situation.

It's also a meme that people will ask the dumbest, most trivial interpersonal conflict questions on Reddit that would be easily solved by just talking to the other person. E.g. on r/boardgames, "I don't like to play boardgames but my spouse loves them, what can I do?" or "someone listens to music while playing but I find it distracting, what can I do?" (The obvious answer of "talk to the other person and solve it like grownups" is apparently never considered).

On relationship advice, it often takes the form "my boy/girlfriend said something mean to me, what shall I do?" (it's a meme now that the answer is often "dump them").

If LLMs train on this...

Not sure what sorts of disinformation campaigns you're referring to...

There is something more interesting to consider however; the graph starts to go up in 2013, less than 6 months after the release of Tinder.