I mean, if using an "irrational" tool to write allows me to write longer, better and helps me think clearer, I'll only call this hobby "irrationally rational" :)

That's a good story but people know good hobbies are not about the tools but the skill.

I also write way more legible with fountain pens and can also maintain/repair my pens, too.

I also take photos and dance. Does this fulfill your criteria for good hobbies? :)