File names with unicode characters are not displayed in the interface, nor do they appear in the coverage statistics.
For example see the Análisis folder of the following project:
https://codecov.io/gh/julienmalard/Tinamit

It works fine on Coveralls (https://coveralls.io/github/julienmalard/Tinamit); see the difference in covered percentage (much higher on Codecov because of the omitted directory).

Thanks!