In fact, when you perform an arithmetic operation on a text string it coerces it to a number. (obvioulsy "abcd" stays "abcd")
If you have a text string like 012345, any arithmetic operation involving this string will coerce it. In your example if you tried C19-Z19 it would work.
OTOH,the comparison operator not being an arithmetic operator does not accomplish this, therefore one has to " cheat" by doing something like *1 or +0 or exp1, etc...
Just be aware that in XL ( as in real life
) what you see is not always what is there.
There are giveaways though. Left aligned cells are text and right aligned are numbers ( if not aligned manually)
The ISTEXT function can help you also.
If you want to know more, delve in the forums, you'll learn a lot