I'm thankful for the returned badges and all, don't get me wrong - for whatever reason, I like hoarding them - but there's no reason to go out of your way to thank me for them.
This has been grating my nerves for quite some years. I tend to leave llama badges to everyone who favourites or comments on my works. It's kind of my way to acknowledge people paying attention to my work without going to their profile to bother them with inane messages - I know I don't particularly like having to hide all those variations of 'thanks for the llama'. They clutter up my space.
Why do people feel the need to leave those? I don't get it. It's just a dumb, free badge - nice to have but not particularly exciting. Takes maybe five seconds of your time. And why should anyone go thanking someone else for adding their picture to their favourites? It's not like they were doing it to be nice to you, they did it because they liked the work. I only ever thank people when I answer to their comments.
I would apologise for being a bitch, but then I'm not particularly sorry. Don't take it too personally, though, since it's my personal pet peeve. For all I know, it's acceptable DA culture to leave those. I wouldn't know, I'm not too entrenched in the community.