When you bookmark a filter, shouldn't it bookmark the parsed version of the filter, not your string? If you rename one of those folders manually, it would suck if the filter didn't update (and other mail systems like Zimbra do this correctly... are you sure Google doesn't?).
Should they all break just because I change the language settings?
"inbox", "trash", "drafts" are labels and localization shouldn't pretend that they are something else.
It is nice if the UI presents us a named shortcut displayed in our chosen language setting, which applies a certain filter on labels when clicked.