Quick note: Now works with the MeFi Modern theme! Please upgrade to version 4.0 if you use Modern. Will post additional screenshots when I next have a chance. (If you use the Classic or Plain theme, and don't use the MeFi Deleted Posts greasemonkey script, versions 2.0 and 3.0 should still basically work.)
Example without the fishy icon script [this is a mockup, not an actual post]:
Example with the fishy icon script in action:
Version 4.0: 2015-05-25 - Rewrote script so it works with the Modern theme. Also now works with Plutor's MetaFilter Deleted Posts greasemonkey script (i.e. the fish icon appears in deleted posts on the front and index pages) -- be sure to run the Deleted Posts script earlier than the fishy icon script.
Version 3.0: 2014-05-23 - Changed script URLs to point to greasyfork.org, since userscripts.org hasn't been stable recently; replaced @namespace with script home page. BTW the profile preference option on MeFi has since been relabeled "Use secure browsing" (from "Use SSL everywhere").
Version 2.0: 2013-07-03 - Now works with the new "Use SSL everywhere" user profile preference for logged-in MeFi members. Also added support for automatic script updates, as well as better compatibility with Chrome.
Version 1.0: 2012-12-25 - Grand opening.
What this script does:
Users who are (1) logged into MetaFilter and (2) have "YouTube & Vimeo video inline?" enabled in their MeFi Preferences will see a small icon adjacent to a clickable link for a YouTube or Vimeo video -- the icon is a typical media "play" symbol (a triangle pointing right), enclosed in a rectangular box with rounded corners.
This script works on MeFi, AskMe, MeTa, FanFare, Recent Activity, and all other subsites that offer the inline video option.
Browser compatibility: Version 4.0 was tested as working in Firefox 38.0.1 and Chrome 43 for Windows. No guarantees that this script will work anywhere else or with other MeFi-related scripts* (e.g. it has not been tested in Opera).
If you'd like to modify the script, please feel free. Disclaimer: I am not a programmer, but if you have suggestions for improving it, I'd be interested in learning about them.
The original fish image design was created by Everaldo Coelho and YellowIcon and licensed under the GNU Lesser General Public License (LGPL). The fish image used in this script is a derivation from a vector version by Wikimedia Commons user Mouagip. I rotated/flipped the fish to point in the same direction as the standard media "play" triangle symbol.