I am wondering, whether what I read online makes much sense in regards to exchanges "banning" mixing services.
I tried it and it seems not. I have tried to mix very small amounts through various mixers and used an account on a major exchange to see wheter they will have a problem with it (as they claim) or not.
Fact is no issues after weeks.
I wonder if in 2021, with the level the mixers have reached with delayed payouts etc., it is still possible to detect wheter a UTXO has been created by a mixing transaction or not.
I have no interest in mixing coins but care for analytical reasons only. I (maybe someone does) would not know what heuristic approach would be working where you don't have uncertainty to an extent where it makes no sense to call it information.
Your small scale testing is unlikely to raise any red flags because so much cryptocurrency is flowing around and intermingling all the time, it wouldn't make sense to ban people for the odd occasion. The people who will feel these sort of bans are the large scale or regular people where almost all of their transactions are inbound from identifiable mixer addresses. We're talking about people who have many dozens of transactions, probably involving fairly large sums, that fit the profile of someone who is trying to clean their money. One of the big benefits of Bitcoin is traceability so if you have intelligence on mixer addresses and have a lot of activity giving you visibility on "normal" transactions (aka a large exchange) then it's theoretically possible to make some educated connections.