I don't believe it's terrible karma. Nothing unpleasant ever happened when I changed the names of three of my horses. I maintained the names of two horses since they were appropriate for them. When I rehome an animal or sell a horse, I inform the new owner that I will not be offended if they alter their name. Most people are happy to do so. I recommend you don't bother changing horse names if they don't fit properly or aren't accurate representations of the breed. Some names are valuable and should be treated with respect. Other names are just nonsense words applied to animals and deserve no more attention than that given any other random thing that people sometimes attach to their horses. If you choose to change the name of your horse, only use terms that are acceptable to you and your family. It's best not to pick a name because you like its sound or meaning. If someone else likes the name, then that's great; but if you can't agree on a name, you'll have to compromise. Changing the name of your horse is not recommended unless it is necessary. If you find that a horse named "Bob" is difficult to handle or is giving you problems, it may be best to give him a new name. However, if he was given this name by someone else, it may be difficult or impossible to change it.