When Is a Baby Name Out of Bounds?
We should distinguish here between honor names and name associations. An honor name, of course, is one you give to your child as a way to show admiration, respect, and love for the honoree. It's a deliberate choice to have your child share his name with someone who is important to you.
Whether you bestow the name exactly as the honoree used it, tuck it in the middle-name slot, or give it a twist to make it distinctive, you are using the name because of the person who bore it—not necessarily because of the name itself. (It's a nice perk if you like the name and the person!)
An association is different. It can be positive or negative: You like the name, but you might not like someone that name is associated with. And very often, we are too quick to rule out names for this reason. If the person in question is no longer part of your life (say, it's a kid from middle school who had a bad haircut), then we should try to let it go.
It would be a shame to rule out a name that you otherwise love because of its (coincidental!) link with someone who isn't important to you. If you give it to your child, he'll quickly erase that link to your old classmate. Spencer will be your son's name, just like Felix is.