I'm not saying this because I'm wearing their signature but all the other links provided have lack of information's and no one actually posted a proof that they got scammed. It's being some years since they are running and advertising on the forums and I see no reason why would scam people over small amounts.
Btcmixer.io looks a phishing site to scam noobs, actually bitmixer.io is very legit, the most famous bitcoin mixer here. We can see their advertisement daily.
I do trust bitmixer.io and it's already popular in the mixing service. And it looks like there are people that wants to use it for scamming people.
Nowadays I saw people that wants to imitate and deceived customers by changing their website address into almost exactly the same one.
And I'm sure that they won't stop as people wants to keep using mixing services.