86 is commonly and widely understood to mean remove from an establishment. 86 as a meaning of kill is a much more obscure and not widely known meaning.
This is not an issue of "can sometimes mean", you are trying to flip the circumstances to make it sound more like a threat.
There are 8647 hats already going up for sale. Maybe in the next few months you can show me a bunch of people getting thrown in jail for reposting or wearing 8647 and prove me wrong.
Comey was the top law enforcement officer in the nation. He joined the U.S. Attorney's Office for the Southern District of New York, where he worked from 1987 to 1993. While there, he was Deputy Chief of the Criminal Division and helped prosecute the Gambino crime family. In case you are unaware, that was a mob situation in which people were often murdered -- i.e. 86'ed.
He had a very long career in NY State and Federal justice jobs.
It's completely dishonest to say he had no idea what the "86" referred to. That's made perfectly clear during his recent apology for posting the image. This was not a share of someone else's post. It was his picture he staged, took and posted.
Unknowns can wear hats all they want -- that's free speech. But a prominent and well-known former FBI director who was at the forefront of the Russia Collusion hoax and who tried to get Trump out of office beginning before the inauguration carries much more serious weight.
People who grab headlines have more responsibility in making sure they aren't crossing a line when they choose to make political posts. They reach and influence far more people than you or I ever will.