Posting images to dA and other sites as clear PNG files without backgrounds and no watermark over them makes your work even more prone to art theft than those without backgrounds.
Here is an example of what I mean by a clear background, this example being of stock images meant to be shared stating “Free for commercial use, No attribution required”: https://pixabay.com/en/water-splash-png-2748640/
Yes, art theft is still happening at the SGC site, which is against the site’s rules 3A and 3B and artists can and should report them. When it is my artwork, I report the thieves to both the SGC site (through Topfan’s management which made the site software) and also Apple’s legal department, which hosts the SGC app, if the thief will not take it down. Apple has a history of both supporting artists and outstanding customer service. The original artist has to do the reporting, as the artists are the ones who can vouch for if permission was given or not.
Unless you intend for your work to be stock, protect it with backgrounds and watermarks.
*Update: I removed the original example links from this post, in case they give other people ideas about trying to take that other artist’s work of her original character. The artist lives in a geoblocked country. Clear PNG files are just too easy to drag and drop. Also, I hope SGC staff will delete the stolen art. The past few months, the mods have been much faster at it and it will hopefully be gone.