tweaks redgifs embed/iframe video
< Feedback on Redgifs Embed Tweaks (RET)
Doing a little investigating, it seems that setting Firefox to block autoplay media on Reddit fixed the issue. Anyone looking into using this should know that the unblur script breaks this script, so you'll have to figure out another way to unblur.
Turning Mute on causes the Autoplay to also be forced on regardless of the value.