Status: OUT
The in-place mutation with return convention forms a coherent repo-wide pattern, but inconsistent mutation behavior across solutions undermines it — some solutions mutate in-place for space efficiency while others create copies for the same category of operation, with no systematic policy governing which approach to use.
The inconsistency belief (currently IN) gates the coherence claim, making this correctly OUT
Depends on (SL): in-place-mutation-with-return-convention