You can also add your own digraphs. I've used this to make entering emojis easier, for eg.
execute 'digraph :) 128578'
so that Ctrl-K :) in insert mode inserts . (`execute 'digraph :\| 128528'` => , `execute 'digraph /\ 128591'
` => , etc.)
Edit: I guess HN strips emojis from comments? Just try these and find out which ones they are, I guess!
This was before I knew that the Julia plugin allows emoji entry too (\:<Tab>), but I still find this more convenient for the common ones because the names of emoji are all over the place.
Ctrl+k a e = æ