I main Kirby in PM and I use it *all the time*, and would probably instantly drop Kirby if he lost it - not that I imagine the devs ever will change a character on that fundamental level unless they sorely needed it/were trying to stop them being a clone of someone else (I figure giving Ganon the float was the final step in separating him from slow/hard hitting captain clone).
Another point I'd like to make is - I use the copy ability at high percentages too, as should anyone who wants to - if you catch them mid stage, get some use out of it, if you want to swallow someone, you're going to need be at the ledge anyway and if you run off you can taunt-cancel to drop it. I've got a fair few surprise edge guards out of running off, taunt canceling and then dropzone-swallowing someone :>
Not to mention, OP saying it just trains people to stay away from the ledge - it gives you a perfect way to interrupt recoveries. You just need to learn where peoples jumps take them/what angles they want to approach from. It's an obscenely versatile move and an absolute staple of what Kirby is as a character, and lets him get away with murder off the ledge as people wind up being terrified of coming near him. Could not disagree with getting rid of it more if I tried.