I've seen it.

They even switched the left and right click

Only like 1 out of all I've seen and I'm left handed with normie setup

I did when I was younger. Had better fine motor skills with my "primary" hand. Eventually as I started playing more PC games and using computers at school more I got tired of always having to move the mouse around and having to reconfigure keybinds for every game (where it was even possible to do so). So I adapted to right handed mouse somewhere around 14 years old.

Beyond that, in my time in IT support, I think I encountered only three people who did left handed mice.

Early in my career I was a sysadmin for a multiuser system, and I often had to go to people's desks to troubleshoot problems they were having. That meant using whatever pointing device and keyboard they had. There were a crazy number of variations, including left handed setups of different types. It was actually an interesting part of the job. But yes, some left handed folks do that, as did some people who had issues with their right hand/arm.

Yeah, some do. It's infuriating to use if you're right handed.

Usually they stick to the abacus

Left handed person here :D I absolutely do, with inverted clicks which drives my coworkers nuts when they need to show me something

That’s probably because the artist is likely to be right handed and so oriented everything to the right hand side of the comic. If they’d oriented everything the right hand side of the characters, that would mean placing everything on the left of the comic, which might’ve felt wrong to the artist.

leftie here. i learned to use the mouse on the right. the number of times my left arm has been unusable, i've been glad i taught myself a little ambidexterity.