To reproduce:
1. Open attached project "PublicPrivateBug.zip".
2. Play "main" scene.
3. In "Game view" click on a "Button", or "Text", or drag "Scrollbar". You will bet a Debug.Log message in console.
4. Inspect any one of those UI elements. You can't reselect the same function which is used, because it is currently set to "private" in "Test.cs"

Actual result: You can use private functions, with Events (mouse clicks, value changes...), but you can't reselect this function.

Expected result: If function is changed from "public" to "private" it should no longer be accessible by the Event. (should change to "No Function", or at least give some error message).

Reproduced with: 5.2.4f1, 5.3.6p7, 5.4.2f1, 5.5.0f3, 5.6.0a6