When I delete a not-an-answer that seems like the poster could eventually improve it into a proper answer, I usually leave a line in my comment suggesting a way they could do so, and tell them to flag it for moderator attention when that's done, so one of us can undelete it. However, it recently came to my attention that users without 15 rep can't do that (and those under 5 can't even contest the deletion on meta). I think low-rep users need a way to communicate with moderators to argue their case if they think the mod was mistaken or to let the mods know that they have improved their answer and it should be considered for undeletion.
I had been thinking we could do this by letting 1-rep users flag their own (only deleted?) posts, but I'm open to other means to achieve this end.