They're calling him 'untraceable' because he was hanging out at a hackerspace and talking about how he didn't want to pre-register for the con because that could be traced back to his real name, so he was going to pay cash. Then someone else was like "bills are serialized, if you really wanted to be untraceable you'd pay with dollar coins like Redacted did a couple years ago," and Quarter Boy was like "I have an even BETTER idea. I'm going to double down for the meme potential," and then put a note in his bag of quarters that said "Blame Redacted, I had to beat his high score," so this wasn't even an *original* troll. He wanted to be a legend and instead became a cautionary tale. He wanted to get laughs and instead he got laughed at. He wanted everyone at the con to know who he was, and now everybody knows he's Quarter Boy.
Legitimately I don't have any idea why he thought this was a funny joke that would make him look good, and there are very few things you could do that would draw more ire from attendees than inconveniencing the volunteer convention staff during the registration rush when everyone just wants to get through the line (and in spite of diverting me to counting quarters and loudly explaining the reason for the delay to the massive line, we managed to get 150 attendees checked in over the course of 25 minutes while ALSO selling 50 shirts).
And I mean. Of course we could have put him aside and counted the quarters later, but then fewer people would have witnessed the legend of Quarter Boy, the untraceable hacker who realized exactly how much he'd fucked up about four minutes into hearing us answer "what's with the quarters?" with "some asshole thought it would be funny" over and over and over again.
You know what *was* a good joke this convention? One guy made stickers that were almost-but-not-quite exactly the logo for a hackerspace (one letter off) and stuck them all over the convention area, prompting outrage and a spur-of-the-moment Easter egg hunt from the hackerspace guys that escalated until he was covering their logo on their merch with his stickers and was using sleight-of-hand tricks to sneak his stickers into their pockets and bags.