i don't care what's in your hair
I accidentally ditched one once. I released it and didn't notice it till after I saved and tried to find it. I immediately restarted my game.
So, obviously, no I haven't, on purpose at least. It feels wrong and such, and I always try to train my starter as much I can because it's usually the power-house of my team until I get some super strong companion late in the game xD