I realized at some point as a leftie I could trivially learn to write a mirror image of what everyone else was writing so learned to write backwards. Since the motions are exactly what others do it’s actually easier in a lot of ways for me. Left handed writing is all scrunched up and annoying, and I got constant smudges on my hand. Frixion ink pens are the only pen I’ll buy because they don’t smudge at all. My guess is it’s actually because it’s heat reactive so it just vanishes on skin, but that works for me! (It doesn’t disappear on the page except the time I put a hot bowl of oatmeal on my hand written deployment reminder notes, which was a bit of a surprise. Took me about an hour to recover gathering data, haha).

I also discovered the mirrored writing thing lol and it made me wonder what ambidexterity is since if ambidextrous people could presumably write non-mirrored with the other hand, aren't those completely different motions that neither hand has had any practice with?

FWIW, you can also put the paper in the freezer and it will become visible again, though usually not as strong as it was originally.

Children have better neuroplasticity but worse persistence than adults.

As an adult I just practiced writing with my left hand loads for basically no reason, it's not that useful, but I still did it for some reason. Now I can write illegibly with either hand :)

Generally agreed, except for the "Anyone" - because people really are different. I'm familiar with a few people (from very young to adults) who are extremely one-handed. The other hand is nearly useless, except for holding and supporting. Those individuals will typically turn newspaper pages or book pages using their right hand (if they're right-handed, and one guy told me that he didn't trust his left hand with a fork to actually hit his mouth, so he used a knife+fork the opposite way of most right-handed people. These people are in a minority, but they exist.

Then there's guitar.. some, or actually most left-handed people can learn to play a right-handed guitar if they simply start with a right-handed guitar. But there are also some people (some of them very well known) who tried learning the guitar for a very long time, and couldn't. Until they switched to a left-handed guitar. (Why it's natural to actually use the left hand for something which looks complicated - fingering, and the right hand for something simple - strumming - has been discussed forever. Apparently that's because a right-handed person typically has better timing in their right hand, and that's why it matters).

As a kid I found it interesting that people pretty much always crossed their arms and/or their legs when sitting on the ground in the same pattern.

After that re-trained myself a few times out of interest to do it the other way around, and one goes through the four odd phases of having to focus on it vs it just happening correctly without thinking about it.

From what I remember it could take 2-4 weeks before you would just do it both without thinking and correctly.