If a video begins playing, it cannot be kept paused. The play/pause control appears only when the video is full-screen. The video can be paused in full-screen, but when pressing the X to close out of full-screen, the video begins playing again.

Scrolling away from the video or navigating to another feed/community does not pause the video either.

This is most noticable on videos with audio, where the audio continues long after trying to navigate away.