I've grown really squeamish about calling people out on these things.
Partly because it stirs up unnecessary drama, and partly because I don't want to come off like some sort of "holier than thou" furry art stalker police, and partly because it doesn't really seem to be against any rules.
The thing is just that I spend an awful lot of time on FA and therefore I tend to recognize certain pictures/characters/fursuits "just like that" (even tho it'd probably seem like I sit and spend hours upon hours scouring the internet hunting for "that one pic that one person on that comparatively small and insignificant furry site have". I'll admit it has happened once or twice, but that's only if it's a style I don't recogize and find myself admiring it to the point of wanting to see more from that same creator.)
Sure, I get not being able to/wanting to draw and/or not being able/wanting to pay for artwork, and I don't really have a problem with people using other people's artwork for avatars and such, for as long as they don't claim it's theirs. And if they take that extra step to provide a proper source for the image, I could hug them.
It's only when people go full "I drew this" and/or "This is my character that I created myself" that I get annoyed.
Some people are really attached to their characters and understandably don't like it when other people "steal" them and completely poop on their backgrounds, personalities, stories and other things. I know this is the internet, but I still like to think people could show enough respect to -not- steal/impersonate people.
These days, the only thing I -will- call people out on is if they "steal" someone's fursuit(s)
Since apparently that happens too, I've noticed, and it's a whole new level of sad when compared to ordinary art theft.