I ran what-cursor-position on a unicode char. Get the following ...

position: 12 of 16 (69%), column: 0
            character: Ő (displayed as Ő) (codepoint 336, #o520, #x150)
    preferred charset: unicode (Unicode (ISO10646))
code point in charset: 0x0150
               script: latin
               syntax: w which means: word
             category: .:Base, L:Left-to-right (strong), j:Japanese, l:Latin
             to input: type "C-x 8 RET 150" or "C-x 8 RET LATIN CAPITAL
LETTER O WITH DOUBLE ACUTE"
          buffer code: #xC5 #x90
            file code: #xC5 #x90 (encoded by coding system utf-8-unix)
              display: by this font (glyph code)
    xft:-DAMA-Ubuntu Mono-normal-normal-normal-*-72-*-*-*-m-0-iso10646-1
            (#x12E)

If I follow the 'to input' instructions ... i.e "C-x 8 RET 150" this
doesn't work. i.e. I can roundtrip and insert a copy of the character I
initially looked up. Needed to do "C-x 8 RET 0150" instead.

The to-input field maybe needs to display an octal string properly
prefixed with a zero maybe?

Rgds,

A.