Was this upscaled from the "child" post given the lack if source?
I found it on imageboards, so I didn't bother sourcing it. I'm not sure, but I don't think it's upscaled - I didn't notice any quality loss, and image size compared to the child's (2.3:1) rules out waifu2x. It's probably just another version that the artist published somewhere else.
I'm reversing the parent relationship as the other post is sourced from what appears to be the original uploads, and this one appears to get a Photoshop of it to remove the background and upscale it.