I donated 1 steem 2 days ago and got 0.001 Steem back every day from @coin-doubler

At that rate it will take 2000 days to double the "investment".

It's kind of interesting how the people who make posts like the above move their money to https://steemitwallet.com/@escrow-services

and they get a higher return than everyone else.

I assume coin-doubler owns your account, escrow-services and everyone who transfers to escrow-services and realistically you get a good return at the expense of everyone else.

I did the numbers for a random account and they made way less than your account did and it took way longer.

I'm happy to be proven wrong but this looks like a bad investment to be honest. if the return was actually true like 100% profit in a few months then you could put loads of money into it