Single characters cannot be searched because doing so would return too many results. In your album, none of the words start with Z but try N, for example.
This really is a surprise to me. I thought that that using a
tag with a name "pete" will only show objects which have the word "pete" but not the word "peter".
And the confusion even gets bigger, because why are all these objects shown by using "N"? Many objects don't start with an "N" anyway.
Just to make sure there is no misunderstanding, I was referring to "tags", I'm not talking about the "search" function.
Cheers, Markus