As far as punctuation, ending periods actually have negative emotion in text vernacular now for younger audiences and should almost never be used in 1-1 messaging. Exclamation points, commas, and question marks, great!
For abbreviations, it's simply know your audience. You should use them when everyone in the room knows them, but you have to think about that first before use. The step of thinking about it is a great mental step to add, but the article presents it more as a steadfast rule. Also, expanding them in parentheses can be a chance to educate your audience for the future even when you have people who don't know, like I'll do below :P
To me, the smallest point was actually the most interesting and valuable, and it was skated over entirely - communicating emotion and sentiment, particularly through emoji use. With WFH (Work From Home) especially, communicating emotion is very socially helpful. I've found a lot of engineers think "well I don't care/need so I'll skip the flowery additions for efficiency" and then leave many non-tech people and some engineering coworkers to decipher if this random slack ask is mad, passive aggressive, inquisitive, or a check-in. This has far worse effects longterm often than an unknown acronym.
Adding emojis can solve this, or if you don't like those, literally giving more social context in words can also do the trick. When we're talking in person, we always communicate emotion, even when it's not the primary purpose. I think many would do well to include that in their online messaging as well :)