[lebca]

I used to know someone wealthy whose continued wealth relied on working with local and state governments. This person's public correspondence in lawsuits and with local government officials was purposefully littered with spelling, punctuation, grammar, and capitalization errors. When I asked them about it, their response was that it was on purpose so that they seemed less smart and thus less threatening, with the hope that they would get more favorable rulings and contracts by not seeming like "one of the big entities."

I'm not asking you to believe me on this, but sharing it more as an anecdote of: something on the surface is sometimes not the reality of what's underneath.

[ddq]

In addition, it broadcasts that the sender is too busy with all their important work to spend time refining and proofreading, that you're getting their raw, unfiltered thoughts directly from them, not through an assistant, and that their time is more valuable than yours so the burden is on you to parse their stream of consciousness jumble for precious nuggets of their exclusive wisdom. The semiotics make sense, plus it's just easier and faster.

[lifestyleguru]

The same with medical doctors. Funnily once in financial subreddit someone claiming to be a doctor from maybe Croatia asked for financial or early retirement advice, but the post was a word salad with misspellings and errors. Commenters immediately reacted that their writing is as illegible as probably their handwriting is, by the way the person reacted one can see that's really a doctor.

Some people have superiority complex and reeky pile of irate thoughts in their heads, and you're very lucky if nothing in your life depends on these kind of people.

[PlunderBunny]

I remember being told that many of the spelling/grammar mistakes in (English) menus for ethnic restaurants were deliberate to make the (English native speaking) customers feel superior.

(Also not saying I believe this at all, just relating an anecdote).