It can be useful under certain conditions. If your wallet identifies your spending patterns, it could estimate the most appropriate size for change outputs so as to fit your next spend size more appropriately. This requires a bunch of analytics first and isn't exactly a perfect science.
This isn't particularly useful long term however, as what erodes your privacy with regards to change is cross spending them to a given service. While on the blockchain it does not appear that you are a single user spending to a single service (since they should give fresh deposit addresses), anyone with access to that service's log will identify yours coins easily.
Therefor a setup where the user can signify which service he is spending to would allow the wallet to single out utxos already tainted to that service, at the same time quarantining that chain of utxos from other services.
Topic: Multiple change addresses (Read 208 times)
What do you think of multiple change addresses? (Not my idea, Electrum has them) Might help obfuscate some cases. On the other hand, it will create more outputs that might be more costly to spend later?
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