Is there a way to exclude a function from auto-completion? Suppose that you are developing a package, and in the next version a function will be deprecated. It is better not to auto-complete it so people do not accidentally discover it and start using it, then get hurt when it is finally removed.
Why do I think that this is possible at all?
There are several System-context functions that do not auto-complete. These are either deprecated ones, or perhaps just undocumented ones. One example is