Before making a deposit from mixed coins, people must do research about rules about mixer, AML, etc. in ToS of that service. If they have rules against coin mixing, don't make deposit with mixed coins, you will take more risk by doing it.
Even without stating the rules, it is what regulators wants, they will surely support the exchange from seizing a mixed coin, the exchange will ask for KYC which is mandatory, or the exchange will permanently freeze the account. It is better to just be careful, this is what I can not read about exchanges, they freeze coin while regulators supports that, be it in ToS or not, but I expect it to be included in ToS. I have noticed that coins from decentralized mixers are the ones that are often seized.