An exchange very well might block you after a coin join. That has nothing to do with coin joins being censorship resistant. Exchanges have never been censorship resistant.
Discussion
Does it happen with the exchanges like Coinbase, Binance? Not to accept bitcoin from coinjoin?
It is probably very difficult to detect since there are only inputs and outputs in a bitcoin transaction and not via a smart contract such as other blockchains
It is pretty easy to detect a coin join from what I understand. The pattern of inputs and outputs is very distinctive. I don’t think major US exchanges are currently blocking coin-joined UTXOs, but I’ve never tried