"Makers leave a log of the movement of funds with the taker..." does this mean that there will be a history of transactions that the maker or JoinMarket will be able to see, and through them, keep records of how you mixed your coins? Is this true regardless of if the mixer is centralized/decentralized?
Takers, who coordinate the coinjoin, pay for the mining fees of makers. This allows the taker to know which equal sized output belongs to each maker since the taker constructed the transaction themselves.
All other outside observers besides the taker do not know which equal sized output belongs to each maker. However, outside observers can usually calculate clusters of inputs belong to the same entity and the change output belonging to that same group of inputs.
Is this true regardless of if the mixer is centralized/decentralized?
JoinMarket uses a decentralized order book for buying and selling liquidity while other coinjoin protocols like WabiSabi use a central coordinator with a timed round to gather liquidity. WabiSabi coordinators do not learn any links between the UTXOs of a user.
"However, outside observers can usually calculate clusters of inputs belong to the same entity and the change output belonging to that same group of inputs." How big of a problem is this?