The buffering animation for loading utterances doesn't show up properly when using the selection player. This is because it shows up when the utterance is fully prepared (has been received from Speechiod) and disappears quickly when the audio starts playing. Moving

mw.wikispeech.player.playUtterance( startUtterance );

out of the callback for the mw.wikispeech.storage.prepareUtterance() on https://gerrit.wikimedia.org/r/plugins/gitiles/mediawiki/extensions/Wikispeech/+/refs/heads/master/modules/ext.wikispeech.selectionPlayer.js#163 should fix this.