I also wouldn't give out tags for this.

The difference in whether or not returns are generated via scam is if they are fixed, consistent, or varying.

Fixed = the biggest red flag.
Consistent = maybe they know what they're doing.
Varying = the most honest response... "We may make money, but there's a chance we could lose it as well."

In the thread in question, the OP could be referring to an average across weeks, months, or years. They didn't say anything about the return being compounded daily; just that they could do trades that would leave them with a 2% to 5% gain over their initial position.

To claim you can do this every single day is sketchy. But to claim this is your average over a year could be reasonable.