I hear you- I'm not a social media person but I get multiple chats via WeChat, Leap, and WhatsApp when my friends and colleagues in Asia wake up. I get Skype, teams, text, and e-mail during the day. It amazes me that kids keep it all straight since they havemany more feeds than I do.
As for the spelling, I blame part of that on the programmers. They fix a word, but put the wrong word in place without any indication that it was changed at all. A quick scan shows readable words, but not the correct words. If they make a change, it should be highlighted so a user can verify the correct word was used. Samsung/Android seem to use a voting system such that misspelled words show up as suggestions. I periodically need to clean out the dictionary to remove them.
That is a good point, spell checker on phones is a huge bane, grrr... 

