Bitcoin on exchanges come from anywhere!
I don't understand what's make it important to know the original source of the coins when you're not doing anything wrong. There's no such dirty or clean coin, coin is a coin, as long as it's not run in centralized network e.g. BSC chain.
exchanges treat mixed coins as suspicious which can trigger the very said investigations.
dont use mixers. you are more likely to not just be flagged for using a mixer,(real world regulations actually state using a mixers is a suspicious activity flag) but also, end up giving into the mixer your clean coins and getting out dirty coins. so get hit twice by exchange monitoring triggers
You make a good point here, it's stupid to use Bitcoin mixer if he's want to trade using a centralized exchange.
But I will not say don't use mixer because if he want to trade his coins using a decentralized exchange or direct P2P, he will not have any problem about the centralized regulation. It depends on each person reference to use Bitcoin.
many people sponsored to promote mixers are LIARS(greedy immoral people that want to use and abuse customers)
they only care about abusing their new recruits for profit and taking their clean coin and handing them dirty coin
yes coins can be classified as dirty.. sorry truth hurts
here is the thing if fungibility was a boolean answer yes/no. or if there was no taint analysis and no such thing as 'dirty' then there would be NO POINT in mixers. but the idiots pretending innocent people should use mixers while saying not to worry about what they receive.. are lying because they want to cheat those innocent people
if coins were all clean no one would need a mixer.. but ironically because these idiots are advertising them they know they need their coins cleaned because there is risk attached to their coins..
the other thing is that the sponsored schemers want innocent people to use mixers because if innocent people did not. then the only pool of coins being used by mixers would be the criminals dirty mixed with dirty still results i dirty
so in short dont trust the words of criminals asking you to hand them your honest earned coins and being handed their illicitly gotten gains..
if their illicit gotten gains were so legit then they would have no need to palm them off to someone else
so just avoid that crap
getting coins from legit services are deemed clean. especially from CEX as they have been vetted as part of regulation. and so exchanges dont put red flags on coins coming from regulated exchanges. but do red flag coins coming from mixers or services that swap AEC coins for regular pseudonymous coins
its worth reading regulators guidance to exchanges to know how exchanges treat coin analysis then you know what to do and not do