I believe you can add notes to cards on the deck builder, but I mean on a card on the inventory.

If there isn't a way to do that, I think that it would add a lot of utility and customization for those that like that sort of stuff. I don't think space is an issue since you can already upload images.

• Lent card to John
• Lent card from John
• Card won from tournament in X place
• Gift from Mary
• Small tear on left side

Stuff like this.