E.g. for c13959 / 565721, https://integration.wikimedia.org/ci/job/mwgate-node10-docker/71325/console says
22:00:58 modules/homepage/suggestededits/ext.growthExperiments.Homepage.SuggestedEdits.less 22:00:58 [2m177✖ Unexpected empty line before closing brace [2mblock-closing-brace-empty-line-before[22m
which is a bit hard to interpret, but refers to line 177, column 2 (based on eslint errors which are similarly garbled but have correct line numbers).
Related: T243115: Output of npm Jenkins tests is garbled
But the line actually violating the stylelint rule is line 407.
Observation (@Demian): stylelint's line counter is often unreliable. At one time it seemed to me comment lines might not be counted, but I didn't verify this idea.
Additionally, some lint rules match inside comments...
Related: T245957: [Development tooling] grunt stylelint gives false positives inside comments, attributed to the wrong line number (tracking upstream reports)