YouTube Link-Player от Ade

This addon allows you to open any YouTube hyperlink as an embedded video. Which saves you the hassle of opening new tabs or windows to watch a shared video, or having to keep leaving and returning to the comment section when clicking on timestamps.

Instructions:

A red button should appear next to any YouTube hyperlink on any page, click it to reveal the embedded video and click it again to hide the video. If a link doesn't have a button, right-click it and select "Youtube Link-player" from the context menu to reveal the video. If a link is formatted as plain-text rather than a hyperlink, highlight it first then right-click it.