Recently I used testdisk/photorec to recover photos from a dead sd card. Made a small donation and sent a big thank you to the developer. As you said, sending appreciations and thanks for someone's hard work is an important thing to do, and if applicable, small donations. Right now I'm quite ashamed I've never did the same for Vim while Bram was still alive, especially since Vim is one of the most important tools I daily use :/.

I have, but it's rare I even know who to thank. Some like Benn Venn (and his joey jr) know they have my undying gratitude though.