Why is RFC 2047/2231 still the default for encoding attachment names?

[Master One]

Interestingly when using the installer, mime_param_folding still defaults to RFC 2047/2231 (MS Outlook, OE) instead of Full RFC 2231 (Roundcube, Thunderbird).

Is this really still a thing?

I mean, RFC 2047 has been deprecated for such a long time and even Outlook > 2007 should support RFC 2231 by now.

I have no way to test it, but I've selected Full RFC 2231 (Roundcube, Thunderbird) for encoding attachment names.