Worrying and potentially libelous. Some countries (e.g. UK) have strict libel law, and by using this you could get Github in trouble for publishing libelous material.
Of course, this has always been possible with git.
Though since GitHub does not have an office in the UK and in the US is protected from foreign defamation judgements under the SPEECH Act, it probably doesn't have much to worry about.
Of course, this has always been possible with git.