It's your tank, your fish. You do what you want. As a person who breeds fish, that fish would not be in my fishroom for long. I would have culled it as soon as I noticed it's deformity. To each his own.

To the op fish with birth defects are cool IMHO. To watch them overcome what is an already fish eat fish world is very interesting to watch. Thanks for posting up the pic of your fish I personally think it very cool looking.
I had a batch of nic fry of which one of them was exceptionally short body. He turned out to be my favorite fish of the batch and I have watched him stand down a full grown red devil who was trying to muscle in on his turf that he had claimed in my 300g.