Thank you. Abbreviations tend to physically shorten text at the cost of cognitively lengthening it. They're useful in cases where space is more constrained than usual, such as on an advertising placard, an axis label on a chart, or the virtual string-space of a tweet. They are also useful in cases such as telegraphy, texting, and some handwriting, where writers are constrained by input difficulty. Where writers are not so constrained, abbreviations act as small disfluencies in otherwise smoothly flowing text. They burden the reader unnecessarily and should be avoided, except in cases such as "etc.", where the abbreviation is the more common form.

Professional writers and editors, and I've been both, have considered this one of the standard "UI design" principles of the field for generations.

(And no, I'm not talking about formal versus informal writing. It's a more general principle, such as using mixed case or putting spaces between words.)

It's easier for me to parse "w/", for the record. You're right that words recognizeable by shape, and "w/" looks really distinct to me.

OP has since reedited their comment --- thank you very much for that, OP!

> Words are recognized by shape, Words are recognized by shape

w/ is both incredibly short and has a very unique shape.

Many people – including people speaking english as second language – are unfamiliar with it.

I, for example, didn’t know w/ meant with until now.

It's pretty common. Now that you know what it means, you'll grow to like it.