I generally don't believe that avoiding clothing that can draw any attention is a good strategy.

I may have phrased that too strongly. The problem isn't that besloganned T-shirts carry a message, it's that that message casts itself too broadly and too obviously to people not in its audience; dog-whistle is common in fashion, but indiscriminate signaling is usually a faux pas. Compare wearing a shirt with a few Western details to showing up in spurs, leather chaps, and a ten-gallon hat.

This is mainly a problem with using text; I wouldn't find it awkward to wear a T-shirt with the skeletal formula of caffeine on it, or an equation I found elegant. Those would get glossed as meaningless symbols to the uninitiated; I'd look nerdy but not aggressively nerdy.