There are some issues with how views and i18n handle text formats and filtering. This is changed in latest i18n dev version, which tries to implement some both more flexible and more consistent text handling, also allowing admin strings (filter_xss_admin).
Related i18n issue (to be released in the next days, so marking this as critical),
In summary, i18n will allow users with the proper permissions (translate user defined strings, translate admin strings) to enter any text as translation but the counterpart is we need to do a proper filtering of that strings later (before we were using locale_string_is_safe() but not anymore).
Consequences: all i18n strings are now filtered (unlet explicitly not, 'sanitize' => FALSE) and if no format available, they will be run through check_plain(), see also
Since views handling of strings is IMHO a bit flawed (yeah, I know, 'administer views' is a 'special permission'), and also 'translate interface' has became one of that permissions we can somehow ease the requirements on filtering translations, but also we should do some minimal (sometimes best-guess) filtering, we can now use 'filter_xss_admin' with i18n strings.
This patch implements that 'last resource' filtering when there's no text format and runs translations that have no text format through filter_xss_admin() which should, on one side, not apply check_plain() to strings with HTML and on the other side, provide some safety.