To each his own. Personally, I think that unless you live in a community where most people have tattoos, the most rational decision is to have no tattoos. I believe they close more doors than they open. Maybe I am mistaken, maybe situations were tattoos help you are more common than I think. Please correct me then.
Tattoos that signal group membership are a costly signal of loyalty, and the cost is precisely closing those other doors. It's just, with the "rationality tattoos", I am not sure what exactly one gains in exchange for paying the cost.
I'd say that a truly rational tattoo is the one that can be easily removed. :D
I could imagine a specific situation where having a rationality tattoo could be the rational thing to do (for reasons other than impressing people who are easily impressed by tattoos), but those are quite unlikely situations. Having a ratio...
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