I interpreted “old reddit vibes” to be more about there being an actual discourse on posts more than being about the subject matter of the posts. If you look at the comments on reddit, they all just agree with each other because they’re the most popular opinions so they get the most upvotes. The thing I like about here is that I can still read that popular comment, but there are few enough total comments that scrolling down a bit leads to discussions that would have been buried in downvotes there. But since they didn’t define “old reddit vibes” I could be misinterpreting as easily as you!
I’m a big fan of contronyms, words with two opposite meanings. I first learned looking for a word to describe the change in “literally” from meaning, well, the literal meaning of something to also the figurative meaning.
Another good one is dust. You can dust your house to remove dust, but you can also dust a cake with powdered sugar.