(gnome-terminal 1.4.0.4)

gnome-terminal can export the selection in UTF-8 format, but the atom for
doing so is called UTF-8 instead of UTF8_STRING which is the proposed standard.

I assume this is a simple thing to change.

To easily test which selection modes are available you can use wish and
type the following while having something selected

selection get TARGETS

for gnome-terminal this gives me
TIMESTAMP TARGETS MULTIPLE STRING UTF-8 TEXT COMPOUND_TEXT

for xterm this gives me
STRING TEXT COMPOUND_TEXT UTF8_STRING LENGTH LIST_LENGTH TIMESTAMP HOSTNAME
IP_ADDRESS USER CLASS NAME CLIENT_WINDOW

UTF8_STRING is also present in other applications, such as mozilla, so it
would be good to have it in gnome-terminal as well.