When applying for a job in academia, shall people specify in the CV if they have got visible tattoos?
Well, consider the possible cases:
Your potential employer considers your tattoo an asset or has a positive bias for tattooed persons. This is the only case where mentioning your tattoo could increase your chances of getting the job, but even then you should ask yourself whether you actually want to be hired because of this.
Your potential employer is indifferent about your tattoo.
Your potential employer has a conscious or subconscious bias against tattoos, but it’s not so strong that they will automatically reject you. In this case, you do not want to inform them about the tattoo early on as it will ruin your first impression. If you make a first impression, you are more likely to overcome the bias and may even sway your employer’s opinion on this matter.
Your potential employer will never hire anybody with a tattoo. In this case, noting the tattoo spares you from wasting your effort on this application. However, it also deprives you of the valuable experience of going through the interview process and possibly a free journey.
You have to judge yourself how likely these cases are in the respective country, but I think it’s safe to say that case 1 is rather unlikely almost everywhere. Also consider that noting something on your CV that really doesn’t belong there leaves a bad impression, even if your employer is biased towards this aspect. I am confident that tattoos don’t belong there in most countries – as they are considered something that should be irrelevant to the hiring decision¹. And even in countries that have a strong cultural bias against tattoos (such as Japan), I wouldn’t expect listing (visible) tattoos on your CV to be the norm given that such norms only arise in frequently relevant cases – which this isn’t, in particular in a country with such a bias.
¹ at least for academic jobs. If you want to work in a tattoo studio, things may be different of course.