When you evaluate code in Clojure files, the result is displayed in the buffer itself, in an overlay right after the evaluated code. If you want this overlay to be font-locked (syntax-highlighted) like Clojure code, set the following variable.
(setq cider-overlays-use-font-lock t)
You can disable overlays entirely (and display results in the echo-area at the
bottom) with the
(setq cider-use-overlays nil)
Out-of-the box CIDER uses the standard
completing-read Emacs mechanism. While
it's not fancy it certainly gets the job done (just press TAB). There
are, however, ways to improve upon the standard completion if you wish to.
icomplete is bundled with Emacs and enhances the default minibuffer completion:
You can learn more about
If you're fine with installing a third-party package for enhanced minibuffer completion you can't go wrong with the modern and versatile ivy.