I have a strong aversion to wearing T-shirts with clever slogans. After thinking about it for a couple of minutes, I think the reason is that there's no good way to filter the message: if a joke falls flat you can avoid making similar jokes, but a T-shirt just hangs around like a dead octopus in a Jacuzzi, slowly growing more awkward and obtrusive.
A LW meetup wouldn't be the worst place to wear that one, but I don't think one would be homogeneous enough that I'd actually be comfortable doing it.
I have a similar aversion for similar reasons, and choose to, when possible, display symbolic representations of ideas/groups rather than specific words; group members or people familiar with the same ideas will recognize them, and others won't.
It would be nice if there were good abstract symbols for LessWrong, rationalism, and/or EA. I've gotten good results from symbols for smaller groups (ex. the fandom for the awesome yet moribund MYST series), and it seems useful.
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