Comment by arjie
I was curious about this a few years ago so I took a look around and found another case, the one of Thomas Wolf / User:Der_Wolf_im_Wald, but this guy seems to be getting away with it because he has a 'no-derivatives' box on the image page. He has the same modus operandi:
1. Post the photo to Wikimedia Commons
2. Mark it CC-BY or derivative (say CC-BY-SA etc.)
3. Have a highly precise attribution clause
4. Sue everyone who uses it without the specific attribution
The funny thing about this copyleft troll is that Someone Who Is Not Him creates accounts on Reddit (e.g. this one[0]) that post exclusively about how they made a mistake and the photographer was well within his rights to sue and you should take him very seriously and negotiate the amount.
> We actually violated copyright law before he wrote to us. So it was our mistake and we apologized for that.
I really should create a List page for this on my personal wiki so I can remember all these guys. I find this kind of behavior galling.
People did bring up this stuff here: https://commons.wikimedia.org/wiki/User_talk:Der_Wolf_im_Wal.....
But since I don't speak German well enough and inevitably this is going to end up in such a situation where you have to, I think it best I don't pursue deletion here. Hopefully a German speaker will see fit, referencing the other cases here.