Meta really wants you to use Reels. Social media consultant Matt Navarra shared a screenshot on Twitter that shows Instagram experimenting with turning all video posts into Reels. So, if your account is public, any user can discover your video and use your original audio to create their Reel. Only your friends will see your video if your profile is private. If you have a public account and don't want your Reel to be remixed, you will need to turn the option off in the Settings or disable it for specific videos.