Byteball White Paper Page 1:
.. Witnesses are reputable users with real-world identities, and users who
name them expect them to never try to double-spend. ..
Byteball White Paper Page 9:
.. some of the participants of our network
are non-anonymous reputable people or companies who might have a long
established reputation, or they are businesses interested in keeping the network
healthy. Well call them witnesses...
(I would also recommend anyone to read till page 11 ..)
ByteFan is posting his witness on a French server in this topic a lot. He registered his account on Bitcointalk just last month, which is no where close to being a reputable person or company. Posting it over and over again seems to be his way to get people to use his witness, but I see no reason for trusting him.
It could be he's just a honest enthousiast, but I can't know for sure.
What would be more interesting is to be able to decide how you can trust a witness. A high level green trust Bitcointalk user could work, but also exchange Bittrex could decide to run a public witness.