pfSense

The XML is gonna happily swallow the <encoding>base64</encoding> tag for pretty much any field type [1] (even those where it makes absolutely no sense, such as checkbox), however, subsequently it will only decode the value for textarea tag [2]. As a result, when you use this in a package somewhere else than in textarea, the value gets base64-encoded on every save. Again, again, and again. It'd be kinda useful to be able to use for other things, such as, hmmmm... passwords that screw up the config.xml when people put special chars in there (which they frequently do).

[1] https://github.com/pfsense/pfsense/blob/master/src/usr/local/www/pkg_edit.php#L228
[2] https://github.com/pfsense/pfsense/blob/master/src/usr/local/www/pkg_edit.php#L738