Re: wicket fence
You've missed another cause: you make a typo, you get the red squiggly line under it, and your right click and pick one of the ones offered -- but you pick the wrong one.
I've done that with some pretty entertaining results.
So the person originally typed, say, oicket. The red lines appear. You click on the wrong spot - you choose wicket, or even ticket, instead of picket. You don't notice and keep moving on.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.