This is just an observation I made while working on this - initially thinking it was a bug in my own application, I've gone back and tested it out further and it's reproducible in the vanilla code.
Note: I'm not requesting or expecting a fix, and the scenario where this is observed is not something I would expect someone to have in place on a live site.
Steps to reproduce:
Allow your guests group to post content
Allow your guests group to upload attachments
Set 'Allowed file types' to 'All files' (alternatively, set 'Allowed file extensions' to allow the upload of video file extensions such as mp3, and audio file extensions such as mp3 or wav)
Access site as a Guest and create a topic
Upload a video file and an audio file in the editor
Click the uploaded files so they are added to the editor
Click the Play button on the video player- video plays
Click the Play button on the audio player - audio doesn't play (in Firefox, you can click the Play button but nothing is heard; in Chrome, the Play button is greyed out)
Submit the topic
Still as a guest, view the topic - click the Play button on the video player- video plays
Still as a guest, view the topic - click the Play button on the audio player - audio plays