From what I've read, lefties are typically classified into "over-writers", "side-writers", and "under-writers". That video caught my attention too, as it shows pretty clearly that he's an over-writer.

I myself am probably somewhere in between an over-writer and a side-writer lefty, edging slightly closer to an over-writer. Maybe a 20 degree angle to the line as my thumb wraps around my other fingers?

I've never found a fountain pen that I've liked because every time I've tried one, I ended up tearing the paper as I go as I'm essentially pushing the nib across the page and so the nib snags on the paper, digs in, and makes little holes. And I left pencils behind as soon as I could in school because every day I'd come home with the side of my left hand silvered with graphite.

These days, my preference is a Pentel EnerGel, a Uniball Signo, or a Pilot G-2 (i.e., gel pens like the article mentions). They can write easily without much force and dry quickly enough so that my hand doesn't smudge. For my daily pocket carry, I've also learned that I always want the capped variants rather the click kind, or else I'll end up with stained inner pockets and scribbles on my thigh. This makes the G-2s nice for home and desk use, but not for daily carry.

(And though the article suggests using cursive and not getting hung up on legibility, somewhere back in grade or middle school I switched to using either print style, or an engineering-hand-like small caps style, depending on mood. Both in the interest of legibility, despite my left-handedness.)