I just discovered
C-x 8 RET as a way to insert Unicode characters by Unicode name or hex code. I have not (yet?) memorised all Unicode character names, so I don't always find the right character.
There is, for example, the character "SNOW CAPPED MOUNTAIN". If I type just "MOUNTAIN" this character will not appear the completion list. I need to remember to search for "SNOW" to see this particular character in the list of completions.
As someone who has become dependent on IDO for anything involving completion, this lack of flexibility is rather unnerving. I use
How can I use IDO-like matching for Unicode input? How can I use flexible completion for ALL THE THINGS?
(I would be okay with abandoning IDO mode if there was something better.)