“No one” in this context meant “no one who actually does maths professionally.”

No it doesn't. Everyone who does Maths professionally does it the same way as in Maths textbooks 🙄

When I see 1+½ i can instantly say “one and a half”

And that would be wrong. It's 1 plus one half. 1½ is one and a half.

when I see 1 + 1 ÷ 2 i actually have to pause for a moment to think about order of operations

You don't know to Divide before Adding??

one I recognize the structure of the problem immediately, and one feels foreign.

Says person with "decades of maths experience outside of textbooks" 🙄

The point is that people who do maths for a living

That would be me

are probably above average in maths, tend to write things differently than people who are stopped their maths education in high school (or lower)

Nope. We all write it the same way as we were taught, even those who have done Maths at University (also me).

these types of memes are designed around making people who know high school maths feel smart

No, they're designed around getting those who have forgotten the rules to argue about it. i.e. engagement bait