First of all, what is "OPSEC"?
Wikipedia tells us that OPSEC is “a process that identifies critical information to determine if friendly actions can be observed by enemy intelligence, determines if information obtained by adversaries could be interpreted to be useful to them, and then executes selected measures that eliminate or reduce adversary exploitation of friendly critical information.”
In the bitcoin context, this means not showing to the public that you own bitcoin. We often consider the devices we use to access our bitcoin as the most common attack surfaces. While cybersecurity should be your top priority, you should not forget about physical safety.
This is where using OPSEC-friendly bitcoin merch comes into play. When you wear apparel with a big bitcoin logo or words like "SATOSHI," "HODL" or "BITCOIN," you are putting a target on your back.
That being said, you can still wear fun and stylish bitcoin merch that doesn't scream "I OWN BITCOIN." It should not be obvious that this is bitcoin merch, but more like an "if you know, then you know" kind of thing.
If you are looking at buying some minimalist merch that only a fellow bitcoiner would recognize, check out our collections at bitcoinshirt.net.