"incorrect" grammar is often intentional. The grammar rules included or omitted is a choice in communication. because the way something is written indicates the way it should be spoken (or thought). It conveys information about the writer and their relationship with the reader - whether it's being written 'casually' as friends would write to each other, or 'formally' as one would write for work or school (or some mix depending on context). Most phones automatically capitalize for the 1st word of a sentence, and people Manually go in to un-capitalize it.
But it's not just formality that gets conveyed because grammatical accuracy and word choice also indicate which items are primary and which are secondary/tertiary/etc. it varies a lot from site to site, like "ML" is an abreviation that mostly just works on Hexbear. also, i, think, there, were, a, couple, books, that, had, a, comma, between, every, word, which, is, sorta, gimmicky, but, they, sorta, read, like, this.