Their voice recognition stubbornly refuses to acknowledge Linux, instead transcribing Linux.
Typing "tboy" or "transfem", common terms in the trans community, gets changed to "toby" or "transfer". I can understand "toby", but the latter is especially bad, as the "r" and "m" keys are nowhere near each other. I'll type these words several times a day, every day, and it'll never get recorded. But one typo of the form "unbeleivalbe" gets permanently etched into the autocorrection.
Any intentionally unorthodox english gets invisibly censored and editorialized. You can say "here come dat boi" nowadays (which is good if you're a fan of 2016 memes) but not "wrasslin". Phrases like "what you doin today" has its tone and informality stripped when it's changed to "what are you doing today".
Options also exist to pre-populate the predictive wordlists with our own terms, and to turn off predictive text altogether.
Predictive text replacements are very bad, but they mitigate the worse issue of the fact that the keyboard is incessantly shifting with every single keypress.