It seems Mp3tag tries to keep files selected during filtering since 2015
[2015-12-06] CHG: file selection state is now preserved when filtering.
But what about after filtering? e.g. If the filter hides a selected file should it still be selected when the filter is removed?
As you can apply actions and other functions to the filtered and selected files and these functions only affect the currently visible selection and not the hidden ones, I would say, that any kind of selection can only work with visisble files.
It would be fatal if you cannot be sure that actions etc. only work on visible files. You would have to remove the selection every time you intend to filter just to avoid any treatment of the hidden ones.
Yes that makes sense. But then what is the purpose of the feature "file selection state is now preserved when filtering"?