The default CKeditor skin, Moono, does not conform to the Seven style guide. We should make a skin that does and enable by default on the standard profile install.
Closed: won't fix
2.0
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It's likely this issue predates Contrib.social: some issue and comment data are missing.
CkEditor 5 has a style that works with any theme; CKEditor 4 LTS has security updates until December, 2028. I would rather not create a style that is useful for no more than three years, considering that CKEditor 4 is probably used from few sites.