If you have a pet with it's original name ,A Horse for example, or managed to name your pet with 2 names in KR BB_Ehanced UI it seems clicking on the name in the pets bar will revert the name to the first letter. If you hit enter this makes the change permanent. If you simply click in it again and hit exit instead this reverts it back to it's current name. In the example of A Horse, click once gives you A, hitting exit reverts it back to A Horse. This can be done as long as you haven't hit enter.
Yes, this is very annoying. I try to rightclick my familiar to release it, and it goes to NAME CHANGE. This has to be fixed prior to mass release (out of Beta). There should be a context if you want to rename the pet.
While we're on the subject, the pet-bar (where name changes take place) doesn't change in size even when it's minimized. So when the pet-bars are minimized, there's an invisible box where you can't put any other items because the always-on-top-invisible pet bar is still there. While it's ok when dealing with one pet, it makes working with a pack quite inconvenient.