My wife's ex-husband also dug a hole. She could never figure it out. Neither could I. He put it right in the middle of the gate to the back yard, like a bear trap. It was easily 2 feet deep by 3 feet across. I filled it in with gravel and dirt. As it was right under the drain spout, that marshy bit of ground became awesomely well-drained.
I don't think you've ever mentioned that your wife was married before. Normally I wouldn't think this were odd at all except that in the photo's of her you have shared she looks so damned young. As for the hole in the yard, have you or lil ever watched the series Walking Dead? There is a scene where one of the characters just begins digging non stop. He begins doing it, so it seems to reenact the burial of his family. -Not sure that's relevant here. I would guess that for some "diggers" it is a manifestation of OCD.
Perhaps someday we could have an anonymous posting function for such stories? mk? I know I have some I'd write up.
Great point. I agree, consider that idea squashed.