Sorry, can't compute...
Can you explain in a bit more detail what you are doing?
From your description, it sounds as if you have set Word to not show hidden
text.
Then you select ("click around"?) some text containing hidden text?
Usually, if you now type anything (tab, enter=para mark, "A"), this would
replace the selection... unless you have "Tools > Options > Edit > Typing
replaces selection" unchecked.
Seems like somewhere along the line, I misunderstood you?