In most cases regarding the taking/stealing/copying of markings, staff cannot do anything. No one can claim ownership to default markings because they are free to the public, meaning anyone can use them to create a variety of designs. When it comes to presets, it works in a similar way, but there are exceptions when we can step in.
First, it's important to understand the nature of the preset that has been "stolen." Was it publically uploaded to a platform, like Discord, where plenty of people could have access to the preset? Was it gifted to a friend? Was it commissioned off? In most cases, if the owner of the preset has simply been careless in the distribution of the preset, they will solely be held responsible for what happens with the preset. (In other words, if Person A shared a preset with their packmates and Person B downloads it, we can't ask Person B to stop using the preset because A intended to upload the preset.)
It sounds to me that you're saying that Person B has created a character that looks like Person A's preset, yes? ^^ It's important for us to know if Person B is using default markings or a preset to take from Person A's preset. If they are using default markings, nothing can be done. If they are creating a preset, we need to look at how B came to know what A's preset looks like. Did Person A give out their preset? Has A uploaded images of this preset online? It is difficult for staff to accept reports like these because it is difficult to provide proof that one design was established before the other.
However, staff can step in if this turns into impersonation. Impersonation involves copying, but there is a distinction-- impersonation is claiming to be someone you're not. If Person B has taken the design of Person A, copied their name and character, and is claiming to be Person A, we can accept this as a report. (Granted, we will need proof that A created the character before B did.)
As for the portion regarding uploaded content to DeviantArt, I should make a note that we can only deal with matters within Feral Heart. If someone has made a character based of a design used with FH markings but the content is contained with other websites (such as DeviantArt), we cannot do anything. Our powers only go so far within our domain.~