I'm not sure what the right component is or who to copy on this bug exactly, but per HTML UTF-7 and UTF-32 should not be supported. Gecko and Presto have disabled these already. WebKit/Chromium would preferably follow us here.
Do you have a test case for out UTF-7 support? That would be a bug, as we were supposed to have blocked it long ago, <http://trac.webkit.org/changeset/49487>.
What is the rationale to ban UTF-32?
ap: from the HTML spec ( http://www.whatwg.org/specs/web-apps/current-work/multipage/parsing.html#character-encodings-0 ):
Support for UTF-32 is not recommended. This encoding is rarely used, and frequently implemented incorrectly.
This specification does not make any attempt to support EBCDIC-based encodings and UTF-32 in its algorithms; support and use of these encodings can thus lead to unexpected behavior in implementations of this specification.
So, the rationale is "rarely used, and frequently implemented incorrectly".
Support of UTF-7 is removed by bug 29078.
But other unrecommended encoding are still supported.
(CESU-8, UTF-7, BOCU-1 and SCSU)
Matrix of supported encoding names per browser is here: