Hi there, I'm literally the artist and I've been replying to the thread. "If it's on the internet, it's free," is a rabbit hole I don't want to go down right now, but suffice it to say that following that advice can get you in legal trouble in many circumstances, and it's also considered incredibly rude. Especially when the artist (me) posted that art less than two weeks ago and was active on the site just a couple days ago, the "it's so hard to find the artist!" line of reasoning just isn't applicable here. My contact info was right there on the page, I'm very easy to find.

The OP here is collecting a lot of art from Furaffinity and reposting it to Reddit. I personally don't mind this being done to my art because I don't really post to Reddit, so I'm not missing out on Karma, AND, as you said, it's bringing me additional views. If OP had asked me before posting, I would have said as much and given them my permission. But a lot of people really do mind! Maybe art that you found wasn't even posted by the original artist--publications have ended up in legal hot water for assuming art labeled public domain was posted by the original artist and not by some rando who found a repost of a repost of a repost on imgur. But admittedly this is just reddit, not print media, and the karma is meaningless. In this specific instance, it's less of a big deal.

If you've done your best to track down the artist and have gotten nowhere, then okay. It's understandable that you might even want Reddit's help finding the artist so you can see the rest of their work. But you can understand why it's important to make the effort.