When I want to autocomplete a word and there are more options then Scintilla displays list with all possibilities. I have lots of autocomplete words with the same prefix, e.g. PhabricatorAudit ... (100s of other symbols) ... PhabricatorWorker. When I write "Pha" then I have two options: Select the right symbol from the very long list or finish writing Phabricator and then write the next letter to narrow the list.
The attached patch improves this by autocompleting the word with the common prefix and then displaying the list. This way, I can type "Pha", Ctrl+Space, "A", Enter and get PhabricatorAudit way faster. It works only with autocomplete.choose.single in SciTE.