[yokai]

Dude seriously... It's "INSTAGRAM".
They lower the quality of any photo. Doesn't matter what type of Image you post.

Stop trying to find flaws on an Instagram photo...

Getting really annoying.

You seriously need to grow up. Instagram doesn't lower the resolutions, you just didn't make your illustrations optimized for Instagram. I even acknowledge that it was because of the service's earlier. If you meet the requirements, then no compression is done to your images. Hence why people who do it at professionally have smooth looking, high rez images on the media. Learn how to learn. (Wow, that sentence was stupid to say, even by my standards.) Though that note still stands, don't use Photoshop and try to mimic vector art, use Illustrator and create vector art.