It's best to include more information on why
It is a person or a group of persons who are professional criminals, probable hackers and are activ in much technical forums, not only in photography forum here or on LL, for example in high-end music forum.
Sometimes they are new members and sometimes they just look for peaple who want to buy something.
I cant write you all here becouse of police investigation.
He use sometimes swedish but mostly german-spainish identity, stolen emailadresses, stolen german identity card that he send sometimes with a photo from him- But it is not him, this photo and this id card copy are stolen!, hacked paypal adress- yes, even this. In soem way he is clever but in other way very stupid.
Mostly he write he would be Geman citizan who live in Spain and talk with strong chinese accent.
how can you avoid him?
- very easy: he have no real knowlegde about photography and the items he offer.
- He mostly offers the items for very cheap prices and hope on greed of the people, so dont trust peaple who sale items to cheap and have no idea of this item. nobody on this planet have a large format lens or an alpa camera and dont know what it is or have much it cost.
- mostly he copy photos from internet of the lens that you look for and therefore thay have very low resolution and bad quality.
- he never write someting in a forum also and afcourse he was never dealing with one memeber of a forum.
I hope he will be captured before he will become more clever.
I hope I can help that nobody in this forum will loose his money.