Your job as a writer is to get your message across clearly and quickly.
One way you can sabotage communication is by laying traps for readers. They stop a reader’s flow as their eye scans over text.
Punctuation – as the name suggests – stops flow. This is why I leave out optional commas.
You can also slow down a reader’s flow when you use capital letters incorrectly. For the same reason you should never write a word entirely in capitals.
Likewise I don’t use the ‘&’ symbol – instead I write ‘and’. The exception to this rule is when the ‘&’ forms part of a company’s name.
The same applies to ‘+’.
It is also better to write out percent in full than use %. Although some newspapers, including one where I work, insists on using the symbol.
Never resort to phone text-style language in anything written for a wider audience. It isn’t funny, clever or useful.