Silent CI checks passed for 30 releases while changelog wrote nothing

A developer discovered that python-semantic-release v10 silently skipped writing changelog entries across 30 consecutive releases, exiting with code 0 and printing no warnings. The root cause was a missing insertion_flag marker line in CHANGELOG.md, left over from a v9-to-v10 upgrade that changed how the marker was configured. A dry-run check meant to verify changelog writes was also found to be useless, as it reported success before ever reaching the insert step that actually fails. Separately, a shell pipeline using tail -1 masked linter failures by always returning exit code 0 regardless of upstream errors. The incidents highlight a broader pattern where checks can be scoped incorrectly and produce the same silent output as a passing check, making them indistinguishable from genuine success.