Consensus is not immutable. Past decisions are open to challenge and are not binding, and one must realize that such changes are often reasonable. Thus, "according to consensus" and "violates consensus" are not valid rationales for making or reverting an edit, or for accepting or rejecting other forms of proposal or action.
Wikipedia remains flexible because new people may bring fresh ideas, growing may evolve new needs, people may change their minds over time when new things come up, and we may find a better way to do things.
A representative group might make a decision on behalf of the community as a whole. More often, people [[WP:PGLIFE|document changes to existing procedures]] at some arbitrary time after the fact. But in all these cases, nothing is permanently fixed. The world changes, and the wiki must change with it. It is reasonable and indeed often desirable to make further changes to things at a later date, even if the last change was years ago.
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