undecided vs utf-8

[Lars Magne Ingebrigtsen <larsi@gnus.org>]

When using erc, it decodes iso-8859-1 fine with the default `undecided'
into encoding.  However, any utf-8 strings are, sort of, just translated
into the same coding system:

(decode-coding-string "u-te-\303\246ff \303\245tte" 'undecided)
=> "u-te-æff åtte"

(decode-coding-string "u-te-\303\246ff \303\245tte" 'utf-8)
=> "u-te-æff åtte"

So, uhm...  Is this meant to be this way?  I know that guessing the
first thing is, well, correct, sort of -- it's valid iso-8859-1,
although very strange.  But it's also valid utf-8.  Shouldn't
`decode-coding-string' prefer utf-8 if it's actually valid?  If it's
valid utf-8, then it's quite likely that it's meant to be utf-8, even
though other coding systems are also possible.

-- 
(domestic pets only, the antidote for overdose, milk.)
  larsi@gnus.org * Lars Magne Ingebrigtsen