Hmmm, you guys are funding traders on Bitfinex? How is that possible and how does it work? Assuming you fund someone who is a trader, how do you know whether they made profit in the trade or if they made loss, and what will you do if the trader never made a single profit from the funds you gave to them??? This is kind of a very risky business to be involved in and I wouldn’t like to do such, unless there is a guaranteed profit.
Simply put: you don't know. Whether it is who the lendee is, and whether he made a profit or not. That's kinda irrelevant.
The only thing that matters is that he's able to pay you back with interest.
That's why he has to put collateral (his margin funds).
Is it 100% safe ? Nope. But it is quite safe, I did it for a few months without any problem or loss.
But unless there's a -80% on all crypto at the same instant, you're quite safe.
Of course, you're still exposed to platform hacking (and the infamous bitfinex haircut style to recoup their losses).