One issue as an editor is bad spellcheckers. When a processor or editing software's spellcheck flags half the words as wrong, you end up missing a few. It gets evenore frustrating when the program doesn't save your additions to its dictionary. I used to run article edits through Scrivener until I ran into one occasion where Scrivener insisted that the words "obsessive" and "denialist" didn't exist. It doesn't explain all typos, but it is a reason that gets brought up in writing circles sometimes.

And just now my phone fought me against "denialist" while not catching my initial misspelling of the word "wrong."